A project
of Volunteers
The Design Refrigerator by:
in Asia
and Develoomen
R.H.L. Exoll, Wijeratna
Published by: Asian Institute Institute P.O. Box 2754 Bangkok Thailand
Sommai
of
a Solar
Kornsakoo,
Powered and D.G.D.C.
of Technology
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of
in any as those
Asian Institute Institute Bangkok
research repori
of Technerlegy T haihand
No. 42
THE DESIGN
AND
REFRIGERATOR
Dr. R. H. B. Exell Sommai Kornsako~ D. G. D. C. Wijeratna
DEVELOPMENT
OF A SOLAR
POWERED
THE DESIGN AbD DEVELOPMENTOF DEVELOPMENTOF A SOLAR POWEREDREFRIGERATOR
Dr.
R. H. B, Exe11
Assistant
Professor
Sommai Kornsaicoo D, G. D. C. Wijeratna
for The John F. Kennedy Foundation, Thailand
Bangkok, February,
Thailand 1936
PREFACE This
research
refrigeration size
describes
system which
will
ice maker or to a cold The subject
Studies Dr.
report
for
his
The Asian Foundation, energy
Master
Institute
Hz E, Hoelscher,
for
Degree
powered
of a ..-illage
preservation.
unit
in his
Individual
was designed
of the unit
by
was by tir.
Sommai
Thesis.
financial
made in response response President
food
and testing
of Technology for
of a solar
to the production
and the experimental
The construction
T'hailand,
research
unit
lead
by Mr. D. G. D. C. Wijeratna
(No. 34).
Report
R. H, B, Exell.
Kornsakoo
eventually
storage
was examined
Project
work on the development
of AIT,
(AIT)
support
is
Foundation.
iii)
to the John F. Kennedy
in the form of a grant
to a proposal to Dr.
indebted
for
solar
made in 1973 1973 by Professor
Tbanat Tbanat
Khoman, Chairman
of the
SUMMARY A small flat
plate
ammonia-water solar
development Regeneration absorption
collector
o f a village takes
the heat
used 3
On a clear
has been tested
during
15 kg of day the
is
No oil
solution
of
the ammonia drops
coefficient
of performance
0.09,
though
at 32'C.
(cooling
effect
is comparable
in the design
(iii)
rises
divided
are discussed.
used.
proposed
from
Rapid by Swartman,
plate.
by solar
previously
are
30°C to 88WC and
refrigeration
The estimated
with
the
46% ammonia in water
During
to -%'C,
towards
a 1.44 m2
at night.
first
containing
with
is
from the flat
temperature
temperature
small
step
or electricity
dissipated
solution
ammonia is condensed
Developments
as a first
the day and refrigeration
C,9 kg of pure
which
refrigerator
by means of a new feature,
of absorption
In the generator
absorption
ice maker.
place
is obtained
in which
intermittent
overall heat
published
the solar absorbed) work.
is
CONTENTS Preface Summary Contents I.
II
III
IV
iii
ii
iV
INTRODUCTION The Basis for Objectives of Possibilities The Rationale
Considering Solar Energy the Study for Research and Development for Selecting Solar Refrigeration
SOLAR FFFRIGERATION Indices of Performance Operation of the Intermittent Ammonia-Water System Analysis of the Ideal Cycle Rigorous Analysis of the Ammonia-Water Cycle Historical Development
13 15
DESIGN OF THE EXPERIMENTAL UNIT Choice of Configuration Operation of the System Concentration of Aqua-Ammonia Regeneration Phase of the Cycle Refrigeration Phase of the Cycle Collector-Generator Specifications The Volume o f the Generator The Size of the Receiver for Ammonia Heat of Generation Heat of Condensation Further Details of the Design
23 23 24 25 26 28 28 30 32 32 33 33
EXPERIMENTAL TESTS Relationship between Plate Temperature and Solution Temperature Experimental Results Amount of Ammonia Distilled Cooling Ratio Heat Absorbed by Solution During Regeneration Solar Coefficient of Performance Discussion
37 37 37 52 54 55 56 56
CONCLUSIONSAND PLANS FOR CONTINUING RESEARCH Conclusions Economic Considerations Modifications The Development of a Village Ice-Maker Alternatives
59 59 59
References
65
Appendix A Charging Appendix B Estimation
- Equipment of Incident
- Procedure Solar
Radiation (iv>
60 60
67
72
-lI The Basis
for
Considering
There are several energy
resource
the countries good solar
of
called
because world
by arid
obstacles
and is
climates
already
distributed nature
have been in smaller
of the
The present aimed at
units
most of the developing
countries
with
practically
by conventional
to this
fits
populations
solar
energy
into
is
users,
for
readily
Fourthly,
the developments
well
means,
all
the pattern
over
the
of rural
Study study
is part
the development
the usefulness
which
need of these supplies
faced
energy
most of
available
to the potential
of solar
as an
and have
is a critical readily
of energy
In contrast
First,
and inaccessible
and are thus
to the provision
energy
to the tropics
distributed,
dispersed
solar
countries.
energy
Thirdly,
capital
of the diffuse
Objectives
AIT,
Secondly,
by electrification
available
considering
in or adjacent
resources.
of investment
insuperable
are
do not have widely
energy
characterised
example,
developing available.
but they
and a lack
for
reasons
to meet the needs of developing
conventional
are
Energy
important
radiation
countries
Solar
INTRODUCTION
and economic
of a project
in solar
energy
of one or more prototype viability
of solar
energy
units for
utilization
in
demonstrating
the designed
purposes, The specific area
of solar
and further, investigation.
objective
energy to select:
of the
utilization a suitable
argument
useful device
in this
chapter
to the developing for
development
is
to
countries and for
identify
an
of Asia, a preliminary
-2Possibilities
for
Solar
energy
and Developnent
research
seems to have gathered
Over this
two decades. and conferences
dealing
comprehensive advisory
Research
with
surveys
panel
period
there
solar
of solar
energy
applications
Developing
Development
entitled
Prospects',
NATIONAL ACADEMYOF SCIENCES (1972).
report
supersede The panel
traditional
using
of earlier
observes
today
on both
to be little this
solar
cannot
by an ad-hoc
Perspectives
The conclusions
and
of this
summarised
below.
has been a historical,
scale as well
it
or brines;
remains There
in many countries. be done by the
industries
process. technology
is largely
to adapt
capabilities
of the
country
such institutions
able
these
established
and the needed development
to use materials
and families
could
The nature
in developing
and manufacturing
Hot water
in question.
developments.
can be manufactured conditions
is well
the technology
anu other with
that
and
International
Countries:
from sea water
and a large
for
and are
evaporation
salt
a small
research
Water heating
hospitals,
schools
become much more widely
of the
countries,
for
equipment
and adapting
is it
avail-
such that
it
to their
seems to be straightforward.
Solar community
that
such surve,s
method of obtaining
important appears
those
is a report
and Technology
for
seminars
One of the m ost up to date
energy.
Energy
the last
have been many publications,
of the Board on Science 'Solar
momentum during
distillation stills
now available
must still
are near for
solar
be regarded
to extensive
stills
that
as experimental
commercial are
serviceable
applications.
but
small
scale
Designs
are
and can be used with
a
-3reasonable involve
degree adaptation
of existing
through
countries materials
or other
more practical improved
manufactured
utilization
Research
of the real
Studies Australian
in air
appears
to be assured;
methods
of obtaining
far
from clear
conditioning
role
cooling
are not
scale
solar
are a substantial application foodstuffs
particular
that
could
lead
could
result
in
to
industrialised
of needs for
with
solar
in meeting
at United
States
is now under energy
immediacy
study.
in developing and extent
in developing
these
Technological
stages.
The
countries.
space heating
energy
entirely
needs. and feasibility The best
countries
of needs
for
are air
known.
to operate
It
cycles has yet
solar
refrigeration
and systems
to be established
refrigerators
number of open questions
has the attractive if
of
of solar
and the
refrigeration.
on which
which
particularly,
have been aimed almost
feasibility
There are many refrigeration for
heating
in early
econom ic
time
for
of research
aimed primarily
are still
at this
ava,ilab le
drying,
of tilese
countries
climates
conditioning
applications
ts for
energy
are areas
extent
or of the possible
countries,
needs of developing
the use of locally
and control
in solar
in the temperate
knows little
would
supplies.
and development
at applications
use of solar
in developing
of food
application
components.
to be dried
applications
in this
specific
to allow
The design
materials
to the
modifications
products.
research
technology
and widespread
of agricultural
panel
design
and locally
A traditional
crops
Further
of confidence
possibility could
that
can be considered what may be the best
in developing
countries.
regarding
refrigeration,
of better
utilization
be successfully
provided,
There and the
of available
-4The possible energy This
conversion
remains
cooking
advantages
developed
trials
if
it
part
of
in India,
acceptance
they
drying,
could
produce
could
useful
and water heating,
solar
cooling
possible
that
energy
is
best
are wide.
for
in
have been providing
extensive
field
in social
rather
area of study.
In order
processes
of development
in
time are evaporation, development
design
the decade.
in
of buildings Applications
should of solar
of new technology.
Refrigeration section
indicates
experimental
that
to be carried
This
and that leaves
to select
out of the solar space heating
Stagej
needs in Asia,
countries
doubtful,
the solar
shortest
and thermal
priority left
thus:
More extensive
development
are in the
are not high
is
cookers
resulted
to a stage
in the
within
Solar
of industrialised
cooking
not
summarised
be brought
in the earlier
applications
laboratories
are
substantial
Selecting
The discussion
or electrical
have so far
heating.
the
require
conditioning
Solar
applied,
results
power will
air
solar
and significant
However,
uses practical
energy
technology
.needs of families,
make some of these
for
in its
performance
and Morocco
or that
solar
The Rationale
energy
technical
at the Panel
distillation
refrigeration,
or electrical
of economic
devices.
are now useful
which
of satisfactory
development
intriguing~problem.
can be successfully
Mexico
The conclusions that
yet
to be simple
the cooking
of these
successful
mechanical
an elusive
appears
to a degree
at least
of the
to meet needs for
conversion Solar
its
applications
conversion
and
to mechanical
out by well-equipped the solar
a device
social
acceptance
refrigeration for
further
of
as development
-5the
following
device food
questions
in developing cooler
section
countries,
or an ice
is devoted
solar
makes the following Maker',
maker?
especially, What size
to an attempt-to
distinguished
What is the need for
must be answered.
find
scientist
Should the device
in Asia? should
it
answers
such a
be?
Ths rest
to these
entitled
of this
questions,
of South East Asia writing
comments in an article
be
anonymously
'A Case for
a Solar
Ice
ANON., (1963).
"After eight years of study of the problems of applying solar energy in an underdeveloped country I believe that the most promising line of research is to develop an ice making machine. The goal should be a self contained, reliable ice making machine capable of making at least 10 lbs. of ice per sunny day at a cost of one U.S. cent per pound using only solar energy and water as inputs, In tropical countries vast amounts of fresh fruit, vegetabies and fish are lost or their value depreciated by spoilage. This spoilage could be prevented by freezing them with ice... Ice is an important commodity of commerce, fetching as much as 10 U.S. cents per pound in remote areas because of its high cost of transportation (due to melting en-route or the alternative high cost of making it locally at the remote place by electricity or fuel), A foreign made electric refrigerator costs about 250 $ LJ.S,, the cost of a comparable solar icemaker would be at least 250 $ U.S. It may seem strange that a solar ice maker costing 250 $ U.S. would be bought when people were not buying solar cookers at only 10 LJ,S, each., The explanation is that the solar ice maker would be bought by traders and shop owners who can easily afford the amount and they would use the ice for preserving their valuable stocks of fresh fruits, fish etc...,.. Also the poor people who produce the fresh fruit, fish etc., can afford to buy ice at about one or two U.S. cents per pound, as it is only a small short-term investment of about 10 or 20 U.S. cents, which they can recover within a faw days after the sale of their frozen products", BA HLI et al.
(1970)
of ice makers in Burma. are assured
of success
also
observe
that
the
size
or of community
have studied They state
purely solar size
from
that
local
solar
facilities
conditions.
for
the
development
ice makers and refrigerators
the meteorological
ice making for
the possibilities
point
of view.
can either The domestic
They
be of domestic solar
ice makers
-6and refrigerators electrically
must be as automatic operated
refrigerators.
have manual participation
because
there
Roughly,
is half
per pound of ice
cent
of the consum er would much higher if
a solar
per pound that
ice
to compete with
solar
ice
would be an operator
of production ex-factory,
the cost
that
under
in Burma for
can
available
of
i,"e in the hand
these
about
for
factories
per pound in the cold
They conclude anywhere
makers
of ice by local but
one U.S. cent
can make ice
season and
conditions,
one U.S.
cent
be a boon to the country.
discussing
countries
cost
season.
could
MERRIAM (1972) developing
be about
in the hot ice maker
the
in order
Community size
each ice maker. U.S.
as possible
observes
possible
applications
of solar
energy
in
thus:
"A very promising application is refrigeration. Refrigeration encompasses household refrigerators, space cooling, air conditioning of buildings etc., but I have chosen to concentrate attention on one particular possible device, a machine for making ice. This is for several reasons, both technological and socio-economic. For one converting the solar radiation into ice solves the problems thing, of intermittency and storage. Ice can be stored for months. Also it is transportable, e.a, An ammonia-water cycle is contemplated. ..*.. Several ice makers and refrigerators using this cycle and solar energy input have been built, The design I have in mind would be constructed of mild steel, and would be rugged and simple without moving parts. The out!ut would be 60-70 kg/day of -1O'C ice, the input would be lo-12 m of solar radiation and the services o f a full-time unskilled operator", The answers
to the
can now be provided, Solar
questions
raised
at the beginning
of this
section
viz:
refrigeration
is one of the most promising
fields
for
further
development; An ice
maker
If
can be made at about
ice
viability
is
seems to be the
assured.
most useful one U.S.
cent
device
in developing
per pound commercial
countries;
-7A community with
size
some manual
development; as far The first conclusions, The next
step size
experimental experience
operation
domestic
objective
is
loo-150
lbs.
of ice
to be preferred
refrigerators
is
that
of the study of selecting
for
a day,
initia
need to be automatic
has been reached a suitable
to make a preliminary
solar
ice maker.
ice maker will for
producing
as possible.
i.e.,
community
unit
further
As a first
be designed
development.
study
device aimed at step
and built
with for the
towards which
the above further
development.
development this
goal
wiJ.1 provide
of an
-8II Some of the performance A brief
theoretical
of solar
analysis
unit
that
will
of the ammA-* ulAra-water
are useful
in analysing
be presented cycle
will
in this
the
chapter.
be made as this
will
be
refrigerator.
of Performance
Any solar
cooling
employti:g
a thermodynamic
conventional focussing
collector index
the coefficient
produced
device
refrigerators,
The usual is
concepts
refrigerators
used in the experimental Indices
SOLAR REFRIGERATION
to heat
refrigerator
essentially cycle
it.
by which
the
of performance supplied.
component
no different
and a solar
to operate
This
consists
heat
is defined
ratio
with
in
a flat-plate
as the ratio
may be applied
may be defined
a cooling
employed
of a refrigerator
same concept
and a cooling
from that
source
performance which
of two parts:
or
is measured of cooling to the
as
heat absorbed by refrigerant during refrigeration heat absorbed by generator contents during regeneration The performance given
of the solar
collector
can be defined
by a heating
ratio
by heat absorbed by the contents of the generator incident solar radiation on the collector The overall
two above defined heat
performance ratios,
ratio
can now be defined
or explicitly
absorbed by refrigerant incident solar radiation
as during refrigeration on the collector
as the product
of the
-9The concepts when analysing Operation
systems
of the
Figures connected
by an overhead
the regeneration
regeneration
phase heat
an ammonia solution rises
and condenses
During
the
is
supplied
is allowed
starts
drawing
Analysis
Fig.
2,2,
of the
Ideal
In the thermodynamic
following processes
contains
to
heat
pressure
contains
phase.
cool.
is reached
which
is
The pressure
in the generator-absorber until
all
is
which
is heated
the
ammonia distills
are assumed to be reversible,
off of
removed and the drops thus
and the
ammonia
producing
cooling.
absorbs
the
the ammonia in the
of the ammonia-water
the
contains
evaporated condenser
Cycle analysis
into
During
immersed in a bucket
source
from the surroundings
continues
aqua-ammonia
system can be divided
As the solution
phase the heat
generator-absorber
ammonia and the process
two vessels
to the generator-absorber
concentration,
refrigeration
The weak ammonia solution
of
phase and the refrigeration
of high
evaporating
separate.
hand vessel
aqua-ammonia
in the evaporator-condenser 2.1,
are
conde nser-evaporator
and once condensation
Fig.
evaporated,
The left
of the intermittent
two phases:
useful
System
hand vessel
as the generator-absorber. as the
are especially
system consisting
The right
pipe.
ratio
and generator
Ammonia-water
and 2.2 show a simple
The operation
water,
and cooling
where the collector
ammonia and functions
pressure
ratio
Intermittent
2.1
and functions pure
of heating
absorption
cycle
all
is
- 10 -
Condenser ~hfmnia --a---
Aqua Ammonia----__
----a_ ---
-
---
Coaling Water
Fig. 2.1 - Operation
of
the
Regenemtion
LCooling
Fig. 2.2
Operation
of
the
Refrigeration
Phase
Water
Tank
Phase
- 11 Energy
is
transferred
in the
form of heat
at three
temperature
levels
i.e., atmospheric condenser
It
at which T a'
heat
is rejected
in the
from the cold
chamber
and absorber,
the temperature
at which
heat
is
the temperature
at which
heat
is received
is possible
a function
equivalent
reversible
heat
rejects
temperature
heat
to imagine
an arrangement
to that
of the absorption
engine
receives
a quantity Ta while
at a temperature
taken
in the generator
of reversible plant,
of heat
producing
machines
Fig.
cg
T performing
Firstly,
2.3.
and
Q, at a temperature
a quantity
of work
a
ga
with
an efficiency,
g - Ta
ga Q, where all
temperatures
Secondly, and rejects
a reversible
heat
of performance
are measured
ca If
can be defined
becomes,
receives
absorbing
refrigerator
-Tc
is made equal ISa absorption refrigerator, plant
refrigerator
at Ta while
of the
on the thermodynamic
a quantity
temperature
a quantity
scale.
of heat
of work Wca
Q, at Tc
The coefficient
is
= to - W ca'
this
The coefficient
as 9,/Q,,
which
plant
will
be equivalent
of performance
on combining
to an
of the combined
the two previous
expressions
- 12 -
/““/‘/{/“‘/“‘J
RI
+--
d--
Fig. 2.
~&dent
Absorption
Heat
Engine
Refrigerator
Machine
C.O.P.
=
Tc(T - Ta'
Qc/Qg
T
-
Tc)
g
The practical under
importance
consideration
of this
result
is that
is known Tg may be calculated,
if
a C.O.P.
since
Ta is
for
the cycle
fixed
and Tc is
chosen by the designer. Rigorous
Analysis
of the Ammonia-water
CHINNAPPA (1961),
a rigorous
Two forms of the cycle
ammonia cycle, actual
presents
cycle.
These two cycles
cycle
in Fig.
2,4
theoretical
may be designated
represented
in Fig.
Even though difficult examined
to realise
temperature refrigeration
t
is which takes
The expression
with
the aqua-ammonia The first
pressure
the
absorption
system
form of the cycle'
The second form of the
temperature
absorption
cycle'
and is
pressure
cycle
is
the more efficient
Hence, the constant
one it
is
cycle
is
temperature
detail., temperature
absorption
In the
refrigeration
1-3 and 3-4.
4-6 the solution
for
comparison
chart.
by 2-3-4-5-2.
in practice.
In the constant processes
for
aqua-
2.4 by 1-3-4-6-1.
the constant
in greater
'constant
'constant
of the theoretical
are suitable
(p-t-X)
may be designated
and is represented
analysis
are shown plotted
on a pressure-temperature-concentration theoretical
Cycle
cooled, is place for
usually
equal
initial
the process
regeneration
phase during
by immersion
to the
during
cycle
6-l.
the amount of refrigeration
the cooling
in a water
temperature
is
consists
tie
bath,
to
Effective
of two process
350
300
250
IL
200 150
100 LL Ol f! 5og
-50
Weight
Fig. 2.4 -
Fraction
of
Ammonia
Ammonia
in
Saturated
Absorption
Liquid
Cycle
where mean latent
Lm w;,
weight
=
The heat
heat
on the
supplied
during
of the refrigerant
refrigerant the
at point
regeneration
w1HvdW
W4H4 - wlHl
during
the process
6-1.
6.
process
l-3-4
is
given
by
9
w4
where weight
suffix
of the solution,
indicating
the point
of the
cycle, specific
enthalpy
suffix
of the solution,
indicating
the point
on the cycle, specific
HY
dW
differential
Thus the expression
W4H4
Historical
enthalpy
for
of the vapour
boiling
out of the liquid,
mass of the vapour
boiling
out of the liquid.
the C.O.P.
- WlHl + /" ' HvdW w4
Development
According
to the
Survey
of
Solar-Powered
SWARTMAN,HA, and NEWTON(19731, of solar Florida
energy
for
by Green.
by heating parabolic
becomes
water reflector.
refrigeration
the
first
Refrigeration study
was probably
undertaken
in a pipe
placed
out by
to explore
the use
in 1936 at the University
The steam to power a steam jet flowing
carried
at the
refrigerator focal
line
of
was produced of a cylindro-
- 16 Oniga reported parabolic
in 1937 that
reflector
to an absorption
beyond the experimental Kirpichev an assembly
type placed
at
conceded very
by a heat the
focus
that
high
of
are unfavourable built,
there
reported
tried
but
to adapt
the system never
successful
operating
of a large
equipment,
has been little
of
got
However,
of solar
and the complexity future
interest
it
energy
ice
per day
by a boiler
has been generally
in producing of this
development. shown in this
of
vapour-compression
on the steam produced
mirror.
in the
operation
250 kilogrammes
were of the conventional
engine
factors
the
producing
the low efficiency
cost
refrigerator
refrigerators
The refrigerators
driven
in Brazil
stage.
aud Baum of Russia of solar
in 1954.
researchers
power,
type Since
the
of syst@, this
direction
system was
of solar
refrigeration, The first
major
project
system was undertaken general
set-up
solution
line
to flow
vapourized
in the boiler
evaporator
is a coil
daily
production
per square
which
metre
absorption
has these
from a cold
cf a cylindro-parabolic
cylindro-parabolic
solar
byTROMBE and FOEX (1964).
of the system,
is allowed
the focai
on an all
is
reflector
of ice was about of collecting
reservoir
through
1.5 m'.
6 kilogrammes
area
for
shows the
four-hour
ammonia-water a pipe
placed
at
Heated ammonia-water
condensed
the container
measured
2.5
main features:
reflector.
subsequently
surrounding
Fig.
refrigeration
in a cooling
used as an ice In the prototype or about heating.
coil. box.
The The
trials,
4 kilogrammes
the of ice
- 17-
----Cooled
Valves
Water
Liquid Ammonia Reservoir
_.. ___------
Evaporator Freezer
-Cold
Chamber
Fig. 2.5 - Intermittent Absorption Refrigerator Built by TROMBE and FOEX (1964).
Solar Heated Water Ammonia Solution
Charging
Cooling Water b:::;;;j :I. A!sF Aimckia Solution
Ammonia
Mode
@
Chilled Water
LiqG Ammonia
Cooling Mode Fig. 2.6 -The Basic Solar-Powered Intermittent Absorption Refrigerator.
- 18 The design
byTrom beand
further
although
boiler,
and condenser, Williams
cooler
modifications
and others
in 1957 intended
consisted energy
accounts
of the
showed that
ether
in an intermittent
absorber with
intermittent
cycle,
built
in this
refrigerator
a flat-plate
measuring
The plate
wassolded
were welded
to headers,
were supported
by strips
as the working
fluid.
Ceylon
and a water
sheet
152,4
intermitten by the
of the
system
Finally,
evaporator.
performance
over
pipe
cooled
6.35
There were three board.
refrigerator
as shown in Fig.
cm by 106.7
to six
of cork
tubing. This
is limited
simplicity
intermittent
was of welded
collector
with
the
R-21-glycol
system.
a simple
at Columbo,
The
2.6.
solutions.
by the use of
in the
food
rim by metal
performance
has a superior
a small
1.27 mm polystyrene
at the
the
obtained
refrigeration
collector
was a copper black.
Although
collector,
areas.
used as working
cycles.
ammonia-water
CHTNNAPPA (1962)
were
be studied
as shown in Fig.
of moulded
can be achieved
low temperature
study
a flat-plate
ether
rural
by a pipe
and stiffened
film
refrigeration
the
built
polyester
refrigeration
for
of Wisconsin
mirror
and R-21-glycol
characteristics
solar
by a parabolic
Ammonia-water
absorption
together
and should
on the
use in underdeveloped
linked
mylar
showed that
promising
may be necessary
for
of two vessels was provided
very
at the University
an aluminized
study
Foex is
and incorporated The solar
absorber.
cm, 0,76 mm thick,
covers
steel
collector
and painted
pipes
on the
An ammonia-water
with
The generator-
2.7.
construction
cm diameter glass
operated
and the pipes
collector
solution
which
was used
Fv
Pressure Gauge
-Boiler Flat - Plate Collector l- ----
t-s
----
Charging Pipe I--
Solution ReservoirVD t - s = Thermometer
Socket
Absorber
Fig. 2.7- Schematic Diagram of Solar Refrigerator Operated with Flat-Plate Collector by CHINNAP PA(1962).
- 20 While
it
has been generally
be more suitable conditioning, it
for tests
is possible
to produce
the lower
temperature
to use a flat-plate
can be produced
in this
showed that
heat
collecting
a simple device
incorporat-ing
in this
such as the
The collector-generator
tubes
and 15.2
and the whole
material
solutions
of
flat-plate
Tests
were relatively
Fig.
2.8
can achieve
of 1.27
cm steel sheet was
cover
on the
evaporation
temperatures rate
schematically. connecting
soldered
to the
insulation Ammonia-
top.
from 58 to 70 percent
evaporator
cooling.
collector
pipes
in a wooden box with glass
but
refrigeration
shows the system
Thin copper
varying
the
ice
a low temperature
a 1.4 m2 flat-plate
with
and a two-layered
due to poor absorption,
that
spectacular,
intermittent
a simple,
consisted
successful;
using
collector
built
was enclosed
concentration
that
the generator
is noted
were not
refrigerator
cm header.
assembly
at the bottom
water
but
investigation
Ontario.
assembly
in air
indicated
with It
would
at one kg a day per 0.7 m2 of solar
intermittent
of Western
collector
required
incorporated
the generator-absorber
at the University
a 5.1 cm feeder
of generation
as low as -12'C.
SWARTMANand SWAMINATHAN(1971) system
flat-plate
by CHINNAPPA (1962)
refrigerator Results
the
collector
at a temperature
surface.
they
that
in the investigation
cooling
collecting
expected
were tested.
were as low as -12OC,
of ammonia in
the
evaporator
was low. Another
study
an ammonia-sodium above.
Results
performance for
for
at
the University
thiocyanate
solution
of the investigation NH3 -NaSCN range
NR3-H20 obtained
of Western in the
Ontario
same system as that
showed that
from 0.11 to 0.27
from the earlier
study,
in 1970 investigated
the coefficients compared with
Nevertheless,
described of 0.05 to 0.14
the system was
- 21 -
Rectifying Column
Charging Line-
Collector Tubes
Vapour Return Line During Refrigeration
Lower Header -
External Return Line
Fig. 2.8 - Intermittent Solar Refrigerator Built at University of Western Ontario by SWARTMAN and SWAMINATHAN (1971)
Top Header ‘-\
Condenser
Fig. 2.9- Solo! Ice Maker Built at the University of Florida by FARBER(1970)
- 22 still
unable
to make any considerable
was concluded also
that
offered
NH3-NaSCN has a better
lower
equipment
to the low volatility was suggested
for
It
energy
intermittent has built
was a compact
source.
Fig.
collector-generator 2.54
cm pipes
ized
iron
a single
the
This
cover
ice
water
42,200
surface
in the
flow
of about
was placed
column due
refrigeration
system
a 6,35
in a galvanized
there
was collected
and 12.5
The solar The
to a 20 gauge galvan' sheet
insulation
metal
behind
components,
box with
the absorber-
such as condenser,
was an ammonia absorbing the liquid
It was reported by the This
that
of
ice
of about
per day and ice
gave an overall
kilogrammes
column of
ammonia and
an average
collector
successful
as solar system,
solar-powered not work
refrigeration but
as there
it
is concenred,
should
be noted
that
were two pumps operated
in areas where
electricity
this the
coefficient
of
per m2 of collector
has been the most
system was not
by electricity.
is not
available
to
as the
cm top header.
and soldered
to the usual
exchanger,
collector
of the system.
of
of Styrofoam
kilogrammes.
0.1
It
of 54%
a flat-plate
diagram
cm centres
evaporator.
18.1
NH3-H20.
concentration
solar
and two pumps to circulate
energy
that
It
per day.
As far
would
heat
was about
performance
unit
type
kJ of solar
produced
An optimal
maker using
shows the
In addition
box,
shell-and-tube
chilled
ice
and one inch
element.
than
did not need a rectifying
the most successful
solar
2.9
at the evaporator.
refrigeration.
were spaced on 10.2
glass
evaporator,
as it
was 1.49 m2, consisting
sheet,
generator
cost
ice
performance
of the NaSCN salt.
FARBER (1970) date.
amount of
totally The system
- 23 III Choice
of
DESIGN OF THE EXPERIMENTAL UNIT
Configuration
It
was stated
earlier
a solar
power unit
and a refrigeration
on either
of two basic
that
a solar
concepts,
refrigerator
The solar
unit.
i.e,,
consists
flat-plate
of
two components,
power unit
collectors
is based
or focussing
collectors. Flat-plate diffuse
collectors
solar
radiation.
provided
to reduce
absorbed
solar
energy
and means are
provided
Flat-plate
are
flat
blackened
Transparent
or control is
heat
covers
losses
converted
are generally
to absorb
direct
and back insulation
from the plate,
to a desired
to remove that
collectors
surfaces
energy, suitable
may be
On the
form of energy, usually
for
plate,
usually
as heated
operation
and
water
heat, or air.
in a fixed
position, The basic a parabolic receiver
flux. the
a small plate
of the focussingcollector
reflector, smaller
energy than
element
to focus
than
the
flat-plate
collector,
experimental
-unit,
collector,
particular
This
focussing it it
of solar
collector
collector
gives
is more difficult
a flat-plate
device,
higher
on
a higher
temperatures Also,
to operate.
collector
e.g.,
radiation
can produce
seems to be more expensive
Therefore,
than the
was selected
for
flatfor
this
study.
The refrigeration absorption
the beam component
the reflector.
Although
is an optical
unit
system,
serve
the
purpose
where
electricity
can be either
The continuous
a continuous
absorption
if
the pumps require
is
unavailable,
the
or an intermitten
refrigeration
power. intermittent
system in rural
absorption
cannot areas
refrigeration
24 The intermittent
system is preferred. regeneration
operations, heating
the
vapour
when the liquid
refrigerant
Since the to keep it
the evaporator Operation
strong
a purely
the
a cooling
by having
function
valve
regeneration, in the generator
to the bottom
header
is mainly
ammonia.
The ammonia vapour of cold
it
was before
cooling
water
heated
the
generator
water
passes
to keep it stops
into
the
was decided is
B is
shown in function
valv e
as
The pressure
regeneration,
Before
removed and valve
and evaporator.
from
which
is
generator
The vapourization
immersed throughout pressure
is now less
is started
the
The condenser pressure
in the than
uniform
in the
due to the
the top
volatility
and the vapour
B is opened.
boils,
The vapour
closed
refrigeration
Ammonia gapourizes
returns
is
and the
collector
pipes.
the condenser
A is
closed,
flat-plate
has a much lower
cool,
The concentration
as the evaporator.
around
the condenser
by the
return
water
drops.
is
place
as the absorber.
insulated
ammonia because
Khen heating
in the generator
vapour takes
it
chosen
A is open and valve
being
by the
top header
the system.
of
System
solution
in a tank
process
effect
device
The weak solution header
the
by the absorbent,
experimental
has been achieved
is
the refrigerant
The configuration
and the generator
of the
During
is
has two major
Refrigeration
producing
re-absorbed
as possible.
Simplicity
3.1.
is
off
container.
vapourizes
refrigerator
as simple
to drive
in a separate
The refrigerant
evaporator.
Fig.
fluid
cycle
Regeneration
and refrigeration.
the refrigerant-absorbent
and condense
refrigeratlzn
tank
than of
now functions
difference
of ammonia absorbs
between heat
from
25
Valve thermometer Ammonia Receiver Coded in a lank of *+ir: Water Safety Valve Upper Hsdler
Eye
-btedRetwn ed G6nerutar ng Aqua nia
Ammda-Absurph-’ Inlets Fig.3.1 -The
First Experimental Unit
- 26 of
the evaporator,
thus
producing
from
the evaporator
passes
through
the surroundings Ammonia vapour bottom the
header
of the generator
aqua-ammonia
covers
solution
so that
thus
until
all
sky from the generator
the liquid
ammonia in the
of operation
has now been completed.
availability
of
solar
and refrigeration
energy,
takes
place
the
to the
bubbles
in it.
through
The glass
the heat of absorption
risers.
Refrigeration
evaporator
refrigeration after
the
the
can be
continues
has vapourized.
To accommodate
at night
effect.
taken
vapour
absorption
so that
to the
the pipe
incoming
facilitating
are removed from the collector
dissipated
the
the refrigeration
A full
cycle
intermitten
is carried
out
during
the day
radiation
is
no longer
available. Concentration
of Aqua-Ammonia
The objective The saturation 45 psia. which
is
vapour
pressure
The temperature
Hence,
at temperature from the
to be 0.46, as point
thus
1 in
Regeneration
p-t-x
of
the absorber
Fig.
pressure cycle
with
diagram
for the
ammonia at this is
aqua-ammonia point
there
evaporator,
tem perature
the atmospheric
the pressure
starting
in the
is
is
temperature an aqua-ammonia
of ammonia vapour the concentration
at 45 psia. is
of refrigeration
found
cycle,
shown
3.2.
Phase of the
The condenser
of 17'F
Thus in the absorber
of 86'F
determining
a temperature of anhydrous
is assumed to be 86'F.
mixture
the
to produce
Cycle
temperature
of anhydrous
is
86'F.
ammonia at this
can be determined,
since
From the p-t-x temperature
the pressure
is
diagram
170 psia.
the saturation Point
and the concentration
2 of (which
_----------------em
---------------------
.-----------m---w-
--.
---_---------------
----__
0.40 XL - Weight Fraction
of Ammonia
Fig.3.2
-
Ideal
0.46
in Saturated
Liquid -lb
Thermodynamic
NH,
Cycle
per
lb of Liquid
-.
17
- 28 does not change cycle
is fixed
collector,
during
which
Refrigeration
which
is
0.40
point
to the absorption
4.
to an initial The cycle
Collector-Generator
Specifications
It was decided frontal
pressure
1 inch
tubes
could bottom
were welded from
area
with
point
header
the
3 and hence
tubes
through
with
feet
of 103'F. 4-l
during
as possible.
corrosion
and 0,06
black.
for
56 in,
length
was half
full.
eyes at both in diameter is
which
a four
Black
ft.
iron
by ammonia-water high inch
ammonia concen-
thick
was used for
was soldered
The ends of the adequate
separation
out of the collector-generator, This
This
Thus,
The plate
intervals.
To provide
when the header
colletitor-generator
at a concentration
the solution.
the necessarily
dull
to headers.
2 inches
process
into
at four-inch
bull's
which
solution'is
the collector-generator.
by four
the top header,
a pipe
of the
four
the
temperature
to resist
the ammonia vapour
of 225 in‘
be observed
arrangement
3 of the
diagram.
as compact
for
and c\'as painted
diameter
was used for
surface
unit
associated
sheet
plate
of the water pipe
determines
by the
reabsL,rbed
to keep the
A copper
collecting
1 inch
is
were used throughout
and the
trations.
absorption
area was selected
pipes
to twelve
attainable
of 45 psia,
is completed
at 17'F
the
Point
phase of the cycle,
pressure
ammonia evaporating
mixture
This
from the p-t-x
the refrigeration
of 0,40 corresponds
seamless
2 are known.
temperature
is assumed to be 189'F,
during
cooled
by four
at point
Phase of the Cycle
Ideally,
fixes
l-2)
by the maxim um solution
the concentration
first
process
of pipe
a 4-inch gave a liquid
The liquid
ends of the header.
and 54 inches
long
shown in Fig.
3.3.
level For the
was used.
The
-
29
-
t -Thermameter
-Top
bd8r
tl56”-y -i--------------
-”
Vapour Absorpkon Inlets ~2” Pipe
Fig.3.3 -
Solar
Collector
l-
- Generator
Do tom Header
- 30 To prevent foam four
inches
and the risers with
heat
loss
thick
at the
rear
was used for
of the collector-generator insulation.
at each end of the collector
polystyrene
foam.
The top and bottom were also
There were two glass
surface
supported
by a wooden frame,
used.
The gap between
between
the two glass
the collecting
covers
co vers
Ordinary tubes
polystyrene
thermally in front
window glass
and the first
the gap was 3/4 in.
insulated of the collecting % in
glass
The glass
headers
thick cover
covers
was' was % in;
were
removable. The inclination horizontal
with
of the plane
the unit
facing
of the generator
was 20 degrees
to the
due south,
The Volume of the Generator The volume dimensions
of the generator
is used to determine
and to determine the
the changes
in
calculated the quantity the liquid
below
from the standard
of aqua-ammonia level
in
in the generator
cycle. Top header 4,667
(half ft
full)
x 0.5 x 000882 ft3/ft
0.206
ft3
0.328
ft3
0.105
ft3
0.639
ft3
14 risers 14 x 4 ft Bottom
x 0.00585
ft3/Et
header
4>5 ft
x 0.0233 Total
ft3/ft
volume
pipe
the system, throughout
- 31Surface
area of the
liquid
in the
top header
half
Lull
ID.x
length
4.026
in x 56 in
225,456 1.565 Specific
volume of aqua-ammonia 1, Vl
0.0192
ft3/lb
point
2, V2
0.0205
ft3/lb
point
3, V3
0.0202
ft3/lb
point
4, V4
0.01895
level Start Its
with
0.639
weight
is
33.281 Increase
ft3
of 0.46
aqua-ammonia
0'.639/0.0192 lbs of 0.46 aqua-ammonia
x 0.0205
in volum e
in liquid
is
level
33.281
lbs
at 170'F ft3
- 0.639
0.043
ft3
0.043/1.565
0.027
ft
0.331
in
0.682 is
at 86'F
0.682
When concentration,
0.46
of ammonia + wt.
Therefore,
ft3/lb
in generator
Thus volume of 33.281
wt.
ft2
at point
Liquid
Rise
in2
of wate
33.281
lbs
wt.
of ammonia
15.309
lbs
wt.
of
17,972
lbs
water
When concentration,
0.40
wt.
of ammonia
11.981
lbs
wt.
of
water
17.972
lbs
weight
29.953
lbs
Total
is
- 32 Therefore,
wt.
After 0.40
of ammonia distilled
the distillation
aqua-ammonia
at
Volume Decrease Fall
in liquid
29.953
lbs of ammonia we have 29.958
x 0.0202
below initial
level
Volume of 29.953
of 3.328
lbs.
below
0.605
Fall
volume at point
centre
is 0,034/1.565
lbs of aqua-ammonia
in volume below
in liquid
level
initial
below
The Size of the Receiver
at 103'F
1 is 0.034 =
ft3.
0.022
ft
0.261'
in.
is 29.953 x 0.01895
volume at point
centre
for
ammonia has volum e
Let the ammonia receiver Required
length
is 0.071/1.565
black
iron
86°F)
= 3.328/37.16
be made of Schedule =
1.015
the ammonia receiver pipe,
0.045
ft
0.544
in,
3.328
lbs
0.089
ft3.
Ammonia
= 0.089/0.0882
Consequently, &inch
(at
ft3
1 is 0,.071 ft3.
Weight of ammonia distilled This
16 inches
40, 4-inch
ft
pipe. 12.18
in.
(condenser-evaporator)
was made of
aqua-ammonia
=
long.
Heat of Generation Let enthalpy enthalpy
of 3.328
(approximately) enthalpy
of 33.281
of
ft3
0.568 Decrease
lbs
139'F
=
in volume
3.328
of 29.953
lbs
of 0.40
lbs of ammonia vapour
at mean generation
178'~ lbs
of 0.46
at 189'F
aqua-ammonia
at 86'F
H3,
temperature =
HA,
=
Hl.
- 33 From fig.
3.2:
33.281
Hl
Therefore, Daily
heat
global
=
Btu.
x
627
2086
Btu.
29.953
x
75
2246
Btu.
6162
Btu.
of generation
solar
-1830
3.328
HA H3
r:
x (-55)
=
radiation
H3 + HA - Hl
on horizontal
400 Cal.cm. -2day
surface
22,800
Btu on
4 by 4 feet per the
Therefore,
solar
energy
incident
generation.
on the collector
is
3.7
-1
surface
day
times
the heat
of
7.
Heat of Condensation After Enthalpy
rectification of 3.328
the ammonia has a temperature
lbs
of ammonia vapour 3,328
Enthalpy
of 3.328
temperature Total
lbs
heat
of
3.328
condensation
The condenser it
in 135 gallons
cycle.
Details
A l-inch A 28 in,
length
as a rectifier line
=
was kept
of pipe
120'F 2110
x 634 at pressure
170 psia
x 138.9 2110 - 462
at a temperature
(80 x 80 x 80 cm3) of cold
The water
Further
at temperature
of ammonia liquid
86O~
of 120°F.
tank was supported
constant water
within
during
Btu.
and 462
Btu.
1648
Btu.
l°F
by immersing
the generation
by a wooden stand.
the Design was used to connect
of this
pipe
rising
to remove water
was made of 4 in pipe
from
connected
the generator
vertically
to the ammonia reservoir.
from
the top header
the ammonia being to the bottom
distilled.
header
was used The absorption
as shown in Fig.
3.4.
.--.-- -
.--a------------1
IL3 I> me --
35
Fig.35
- Solar - Powered
Refrigerator
36
There were two ammonia shut-off pressure
in the system was indicated
was attached leading
to the generator
to the ammonia receiver.
valves
to control
the
by two bourdon-type
and the other
was at the
A thermometer
system.
The
ammonia gauges; top
was also
one
of the tube used at the top o
IV Relationship
Between Plate
Temperature
The collector-generator were made to find
and solution
temperature
It
that
at
plate
The average This
values
calibration
that
charged
water
with
between
tests
solution
Lhe plate
and end of each day both
temperatures
was necessary to the
differences
because
generator
it
pressure
measuring
(see Fig. than
the
was observed
shown in Fig.
thermometer
internal
(T
were the same.
TP-TL are
no high
for
out
was lower
However,
temperature
temperature
runs were carried temperature
by about
and temperature
2.4'F.
of the
had been attached
Five the
temperature
the beginning
Temperature
the relation
(TL)
was concluded
corresponding
and Solution
was first
meazarements
4.1).
EXPERIMENTAL TESTS
4.2.
fitting
temperatures.
Results
EXDeriUEntd
After
evacuation,
(see Appendix Figu:es
4.3
A).
temperature
(TL) derived
and condenser The evaporator absorption
(Pl),
solution respectively
in
from
water
pressure,
are shown in Fig.
four
runs
on nearly (Tp),
the
are shown in days.
the solution 4.2,
when leaving
during
solution
cloudless
shown in Fig.
temperature (T3)
aqua-am monia
test
temperature
the calibration
temperature
0,46
the solution
rectifier
generation
(T2),
period.
evaporator
temperature
derived
from the pressure,
and absorption
temperature
for
refrigeration
4,4.
The theoretical
the collector-generator in Fig.
during
4.3 are the plate
ammonia-vapour
cooling
pressure,
obtained
with
These runs were performed
in Fig.
pressure
system was charged
The results
to 4.14.
Illustrated
vapour
the
4.5
are
and actual
the
cycles
shown as l-2-3'-4'
executed
period by the
and l-2-3-4-5
(April
22,1975)
30 1 lo
I
9.00
IO.00
1
I
I
II.00
I
12.00 12
25 Time - hrs
Time - hrs
(April
438.00
I 9.00
I
1 1 10.00 Time-hrs
(April
24,1975)
8 II.00
I
12.00
Time - hrs
IL 90 ?!
2 80 al k70
(April
18,1975)
p 65 Time - hrs
Fig.4.1 -
Observations
on
Plate
and
Solution
Temperatures
23,1975)
“C
3@. 2
e e@@ee
ee @e
0 -I zoo
8.00
9.00
10.00
II.00
12.00
13.00
14.00
15.00
16.00
17.00
Time - hrs
Fig.42
-
Differences Five
Test
between Runs.
Plate
and
Solution
Temperature
( Tp - TL ) : Mean
of
l9C
-
2a
18C -
24(
17c
2a
.
16c IX l4C
2a .
l8C I6(
IL
= Plots
, I30 aa
. .E 14(
Temperature
= Solution
= Solution Vapour Pressure = Ammonia Vapour Temperature
2120
Leaving ;
Temperature
II0
Rectifier
Condenser
Coaling
Water
Temp.
IO0 90
6(
80
4c
70
2c 1
60 7.00
Fig.43
I 8.00
- Observations
I
9.00
IO.00
during
11.00 Time - hrs
Refrigeration
I
12.00
Test
I
13.00
on
May
I
14.00
9,
1975
15.00
16.00
-
41
-
-
‘0
42
-
aJlI+DJadUJCtl
24r
18l
IL
2of
i7(
I81
Ia
l6(
Plate Temperature Solution Temperature Solution Vapour Pressure
15
Ammonia Vapour Temperature Leaving Rectifier
s l4( tI E” l3f If!
Condenser Cooling Water Temperature
r3
12(
4’
T-
IN
6(
lof
4(
9(
2f
--
k-----x
6( 7(
8.00
9.00
10.00
I
II.00
12.00
13.00
I
I
14.00
15.00
Time - hrs.
Fig.4.6
- Observations
during
Regeneration
Test
on
May
IO, 1975
16.00
17
Evcporrrhx
Pressure
r
Evaporator
Absorption
Pressure
TemDerature
60-
50
3OL
Ul 0
IOI
20I
30
40
50I
60I
70
Time - min
Fig.4.7
- Observations
during
Refrigeration
1
Test
I
1
100
90
80
on
May
II0
120
IO, 1975
130
I%
33 OF
----__
l8C TO =F I60 I50 h Ol
140
5
I30
&
I20
Theoretical
Cycle -4
-Actual
Cycle
II0 )2OF
-w-----m__
90
O°
VP--_
-we--__
80
go;
---_-
.
._
70 60
0.36 XL
Fig.4.8
0.38 - Weight
- Actual
II 0.417
0.40 Fraction
and
of
Ammonia
Theoretical
I 0.46
0.44 in
Saturated
Solution
Liquid
Cycles
0.48
-lb
for
NH3
per
Test
0.50 lb
of
on
0.52
Liquid
May
IO, 1975
26r
18(
= TL T2
=
T3
=
Plate Temperature Solution Solution Ammonia Leaving
Temperature Vapour Pressure Vapour Temperature Rectifier
Condenser Cooling Water Temperature
8( I
700
8.00
9.00
10.00
II .oo
12.00 Time
Fig.49
- Observations
during
Regerwation
13.00
14.00
15.00
- hrs.
Test
on
May
14, 1975
16.00
17
( I69 psia)
9’ Absorption
Temperature
IOC
.::
9‘ 80
In 0) 70
60
3(
Evaporator
Pressure ( P3
Evaporator
Temperature
2(
I(
Absorption
10
Pressure
I
20
30
40
1
50
60
70
80
90
IO0
II0
I20
130
Time -min.
Fig.4.10
- Observations
during
Refrigeration Refrigeration
Test
on
May
4,
1975
I40
I
- 48 -
201 19(
IA
.
26
l8(
24(
l7(
22(
l6(
20(
l5(
l8(
l4(
Piate
l3C 12c
Ammonia Vapour Temperature Leaving Rectifier Condenser Colling Water Temperature
Fi g
Temperature
Solution Temperature Solution Vapour Pressure
IIC IOC
8(
9c
6(
8C
4(
7c
2(
8.00
9.00
10.00
Il.00 Time
Fig.4.12
- Observations
during
12.00 -
13.00
14.00
15.00
hrs.
Regeneration
Test
on
May
17, 1975
16.00
69 psia) I3
I2
9(
IO
7(
-~-~~x=.---x-
l-
x-v
Absorption
Temperature
-x-----X-----
LJl
61
Evaporator
3(
Pressure
Evaporator
Temperature
-L-m 5(
4(
2c Absorption
IC
3(
I 10
20I
Pressure
301
40I
50
60
70
I
80
90
100
II0
120
I30
17,
1975
Time -min
Fig.4.13
- Observations
during
Refrigeration
Test
on
May
140
I50
91 OF
Theoretical
--_-
‘< c-
Cycle -1
Actual
Cycle
l-
-----I.
0.34
0.36
3.38
XL -Weight
Fig. 4.14
Actual
0.40
Fraction
and
of
32OF 34OF
0.42
Ammonia
Theoretical
in
0.425
0.44
Saturated
Solution
0.46 Liquid
0.48
- lb. NH3
Cycles
for
0.50
0.52
per lb. of Liquid
Test
ivo. 6
(May 17,1975)
- 52 The analysis is
given
of the test.on
May 14th
1975 (Figures
4.9,
4.10,
and 4.11)
as an example below,
Amount of Ammonia Distilled Initially
we have: Concentratfon
33.281
lbs
Weight of ammonia
15.309
lbs
Weight of water
17.972
lbs
Total
After
regeneration
generator
weight
is 0.416,
the weight
Therefore,
of solution
the final
concentration
as shown in Fig.
Weight Since
of the solution
in the collector-
4.11,
Weight of ammonia of ammonia + Weight of water
0.416 17.972
lbs,
Weight of ammonia in solution
12.800
lbs.
amount of ammonia distilled
2,509
lbs.
of water
The amount of ammonia distilled level
0.46
of solution
Fig.
in the receiver.
was also 4,15
determined
by observing
shows the
geometry
area of the
liquid,
of
the liquid
the cross
section,
of the receiver, Let
A
be the cross
section
R
be the radius
of the receiver
h
be the height
of the
liquid
of
receiver;
cross level
section, above the center
receiver, 1 also,
let
be the v
length
be the volume of
Then the volume
of the liquid
the
the drain is
equal
pipe to Al +
below
the receiver.
of the
Ammonia
I
\-
-
-\--
-.
--
--.---L:--.L-----
~
--
--
-
+-.p-&-----/
--
-~I&z-iygz;;/ --
z ---- --- -.-. -
__
~
Receiver
-
--
zJ”s-I/
--I---
-..-+----
-ii-\/
Bull’s Eye
Drain
FULL
Fig. 4.15
-
Valve
SCALE
Cross - Section
Ammonia
Receiver
where A
+ h k???
= 2.013
We have after
8R2
=
this
run
inches,
volume of liquid
after
1 = 1.25
h was observed
volume of liquid This
+ R2 arcsin ft,
1
and
v
0.0666
ammonia distilled
the vapour
the regeneration;
0.00105
tuft;
and
This gives
to be 0.3 inches.
ammonia was observed
=
tuft.
at 7.00 am in the morning
pressure
of the ammonia was 169 psia.
We now have from the ammonia tables: 86'~
Ammonia temperature Density Therefore,
weight
This calculated
of
liquid of
confirms
Cooling
the
2.509
concentration
thermodynamiccycle
Ibs.
lbs
previously
solution. in
the generator
as shown in Fig.
If
2.48 is
lb
of
0.4165,
4.11.
Ratio
The cooling and is
the quantity
in the ammonia-water
the final actual
with
lb ft-3 2.48
ammonia distilled
the change
ammonia is distilled, this
liquid
is in good agreement from
37.16
ammonia
ratio
defined
as
Cooling
ratio
of the
=
n
cycle
measures
the
performance
of the
system
55
lrhere Qc
cooling
Qg
heat
The cooling
available
absorbed
available
during
refrigeration
period,
by collector-generator
during
refrigeration
during period
and regeneration.
can be calculated
as follows. 2.509
lbs
of liquid
ammonia at 86'F
2.509
x 138.9
348.9 2.509
lbs
of ammonia vapour x 617.5
by Solution
193'F enthalpy
of
180'F and enthalpy
at 19'F has enthalpy Btu
During
of 30.772 =
H3,
2.509
lbs
=
HA,
of 33.281
lbs
86O~
Hl,
=
- 348.50 Btu
1200.8
Let enthalpy
Btu
obtainable 1549.30
Heat Absorbed
has enthalpy
Btu
1549.30 cooling
psia)
Btu.
2.509
Therefore,
(169.2
lbs
Regeneration of 0.416
aqua-ammonia
of ammonia vapour
of 0,46
at
at mean generation
aqua-ammonia
at
temperature
From Fig.
4.11,
Hl
33.281
HA
2.509
H3
30.772
Total
heat
-1830
x (-55)
Btu
x (625)
1568
Btu
x (79)
2431
Btu
absorbed
by solution
H3 + HA + Hl 5829
Therefore,
cooling
Btu
1200.8/5829
ratio
0.209 Solar
Coefficient
of Performance
The solar
C.O.P.
is
to the amount of solar of the solar
defined
energy
shown in detail
in Appendix
energy
by the
absorbed Therefore,
absorbed
absorbed
energy
solar
as the ratio
of
by the collector
by the collector B.
the cooling
plate
plate.
13,237 Btu.
C.O.P.
1200.8/13,237
The amount
can be calculated
For the run on May 14th
plate
obtainable
the amount
as of solar
0.0907 The results
of all
four
experimental
runs
are summarized
in Table
4.1.
Discussion Although are still
the
system has worked,
low as in
the previous
and SWAMINATHAN(1971). system, there
However,
on the outer
process surface
is
studies
in
was completed
ratio
solar
heat losses
the absorption
process
within
process
two hours took
half
C.O.P.
and SWARTM AN
to control
the refrigeration
of the evaporator
and the
of CHINNAPPA (1962)
difficult
Swartman found
were no such difficulties
The absorption ice
while
It
the cooling
in the to be slow,,
in this
system.
and the formation an hour
(Fig.
4.16).
of
- 57 Table
Summary of Experimental
4.1
Results
9
Date May 1975 10 14
17
Regeneration Initial
mass of soln.
Initial
soln.
temp.
(lb) (OF)
33.28
33.28
33.28
33.28
84
90
86
84
Max. soln.
temp.
(OF)
186
193
194
191
Max. soln.
press
(psia)
196
204
205
202
Temp. of condenser Incident
solar
radiation
Heat to collector Final
(OF)
plate
(Btu) (Btu)
concentration
NH3 distilled
(lb)
80-94
86-93
84-90
87-91
22257
24571
24514
24083
12018
13267
13237
13004
0.44
0.417
0.416
0.425
1.19
2.46
2.509
2.03
Refrigeration Min.
evaporator
temp (OF)
20
19
21
1178
1201
974
Cooling
obtainable
Cooling
ratio
0.120
0.203
0.206
0.167
C.O.P,
0.047
0.089
0.091
0.075
Solar
(Btu)
21.5 570
58
Fig.4.16 - Refrigeration Process - Lower Frost on the Evaporator.
Photograph
Shows
- 59 V
CONCLUSIONSAND PLANS FOR CONTINUING RESEARCH
Conclusions The capability solar
powered
operating design
of AIT in the
refrigerator
conditions
were found
to the bottom
during
to be almost
The theory
The new feature
taken
header
of
the
process
shown to remove the difficulty rapid
Furthermore,
generator is
for
therefore
from the
so that
dissipated
from
with
well
the
under-
evaporator
is
the heat
of absorption
the flat
plate
by previous
satisfactory
of
the
in accordance
is
ammonia vapour
encountered
absorption
exactly
of the system
by which
the refrigeration
sufficiently
and operation
has been demonstrated.
specifications.
stood.
construction,
design,
workers
has been
of obtaining
operation.
Economic Considerations The cost
of making
depreciation
Therefore
However, demonstrate gain of
of
ice
solar
ice
the
cost.
then
the
solar
annual
cost
per
sufficient
radiation
climate
would be about 1 kilogramme
in Bangkok
no attempt
or to minimize
of the
If
bahts.
on a good day is
of ice would
effect
experience;
viable
yield
in making
the refrigeration
system
economically
1 kilogramme
the objective
practical the
and studies
was 15,500
of the cost,
obtained
the average
price
unit
10 percent
effect
of ice,
over one year
the wholesale
times
is
The cooling
to make 2 kilogrammes
per day.
experimental
and maintenance
day is 4 bahts.
show that
this
this
cost
(0.375
bahts
experimental
produced
from solar
maker is within
unit
was merely
energy,
eleven
to
and to
the performance
seems, therefore, striking
is
per kilogramme).
was made to optimize It
This
4 bahts.
of ice
distance.
that
an
60 Modifications Work is at present The first
is
under way to test
an expansion
the ammonia receiver
value
with
a box for making
used to enhance
the solar
the mirror
attachment
will
A solar larger
village
test
a solar
using
oil
generation
will
solution,
a packed column will
domestic
therefore
ice
positions
or village
of
The
use.
and hence relatively
be to design,
100 kilogrammes
of
construct,
ice
per
and
day without A unit
and easy to operate.
per day requires
will
be improved
be avoided
with
the help
capacity separator
The system
by keeping
solar
collecting
instead
in several
heater
of a larger
during
containing will
5.2.
excess
be reduced
diameter
regeneration
is shown in Fig.
High
ways.
the ammonia concentration
of a reservoir
of the solar
be used to save heat
refrigeration,
Various
mirror
metres,
will
constant
The thermal
exchangers
of
for
must be rugged
of the system
temperatures
is a flat
will
5.1,
be more efficient
produces
20 square
in the generator
during
would
It
100 kilogrammes
The efficiency
using
units
maker that
of about
coils
between
Ice Maker
or electricity.
producing surface
ice
connected
feature
the generator.
are shown in Fig.
The main objective
cheaper.
The second
maker may be designed
sized
coil
be tested,
of a Village
ice
of
on the refrigerator.
The evaporator
inlets.
ice.
heating
These two new features The Development
a dry evaporator
and the absorption
be used to cool
two new features
header.
by Heat
and to save cold
Condenser
Packed
Column Ammonia
Separator
Heat
Solar
Hea?er
Fig. 5.2
Receiver
Exchanger
Aqua - Ammonia Reservoir
Proposed
New
Solar
Powered
Ice - Making
System
3’
- 63 during
In the daytime, Strong
solution
exchanger
from
of
static
water,
A is open, passes
and B is closed.
through
and weak solution
the heater,
Ammonia vapour
of the reservoir. cold
valv e
the top of the reservoir
to the bottom
immersed in
regeneration,
from the separator
and the ammonia liquid
the heat
returns
to the bottom
is condensed
in a coil
is collected
in the
receiver. At night, Ammonia from
during
the receiver
B, and the
valve
passes
evaporator, of the
dissipated
heater,
by the solar Also,
cooled
by exposure In this
reported
in
before,
system the
the heat
the
is
then
and the strong static
water
absorbed
the expansion in weak aqua-
of solution
solution
is
returns
surrounding
to the top
the condenser
is
sky,
the workability but
the system
and B is open.
exchanger,
'i'he heat
reservoir.
to the night
literature,
However,
through
A is closed,
The vapour
ammonia from the bottom
of the reservoir.
valve
refrigeration,
is
of all they
the individual
have never
unlikely
units
been combined
to present
has been in
any serious
this
way
technical
problems. Alternatives It his
has recently
group
producing three
are developing 75 kg of ice
times
inherent parabolic
been reported
an ammonia-sodium per day.
the previously
in ammonia-water collector
by GUPTA (1976)
obtained systems
thiocyanate
The design value will
25 m2 in area will
that
R. L. Datta system
coefficient
be'used
for
capable
o
of performance
and the problems
be avoided.
and
of rectification
A cylindrical heating
the
generator.
is
- 64 DATTA (1976)
himself
has remarked
+;lat
"It is much easier to cool to 50°F or 60°F and provide a decrease .oeo. humidity than it is to refrigerate food to ice temperature. Intensive research should 'be directed toward inexpensive 9.. . indigenous equipment to provide such cooling in cellars which Stationary flat plate collectors might be partly underground, with selective surfaces could be used rather than movable and operation by manpower of the developing focussing collectors, countries in their rural areas will be cheaper than automatic There is a machines which require larger capital investment, challenging problem of operating such solar coolers in remote areas where electricity is not available.'.! The remarks refrigeration that
there
touch with to the field.
made above show that
technology are various these
for lfnes
development
the development
use in developing of research
areas
of solar
is an active
to be followed.
and is capable
of making
powered
AIT will significant
field,
and
keep in contributions
- 65 REFERENCES ANON., (1963), BA HLI,
a Solar
(1970),
Possib!lities
Energy
Society
Conference,
(1961),
CHINNAPPA, J. C. V., Absorption
Refrigeration
Cycle
Solar
for
Energy L p.1.
Solar
Australia.
Study of the
Employing
International
Ice Makers.
Melbourne,
Experimental
Systems of Ammonia-Water, pp.
Ice Maker,
et al
F.,
Solar
A Case for
Intermittent
Vapour
the Refrigerent-Absorben
and Ammonia-Lithium
Nitrate,
Solar
Energy
l-18. (1962),
CHINNAPPA, J. C. V., Operated
Performance
by a Flat-Plate
DATTA, C. L.,
(1976),
Working
Paper,
March 1976, FARBER, E. A., System,
Solar Expert
Natural (1970),
Collector, Energy Working
Resources Design
GUPTA, C. L.,
Melbourne, (1976),
Solar
Solar
- Its
1970,
Vol.
6, pp.
143-150.
to Developing
Countries.
Division,
Energy,
ESCAP, Bangkok. of a Compact Solar
International
Solar
Energy
Refrigeration
Society
Australia, Energy
in
India,;Working Energy,
Paper,
Expert
Workin
March 1976, Natural
Resources
ESCAP, Bangkok.
MERRIAM, M. F.,(1972),
Decentralized
Technology
and Development
Series
19.
No.
Perspectives
and Prospects.
Power Sources
Institute
NATIONAL ACADEMYOF SCIENCES (1972),
D. C.
Relevance
Refrigerator
Group on the Use of Wind and Solar
Group on the Use of Wind and Solar Division,
Energy
and Performance
Paper No. 6/58,
Conference,
of an Intermittent
Solar National
for
East-West
Energy
Developing
Centre,
in
Countries,
Working
Developing
Academy of Sciences,
Paper
Countries: Washington,
66 SWARTMAN,R. K., Refrigeration,
HA, V..H.,
and NEWTON, A. J.,
the American
Society
(1973),
of Mechanical
Survey
of
Engineers,
Solar-Powered August
1973,
73-WA/Sol-6. SWARTMAN,R. K., Mechanical TROMBE, F., with
and SWAMINATHAN, C., Engineering,
and FOEX, M., an Absorption
New Courses pp. 56-59,
June 1971, Vol. (1964),
Machine
of Energy,
(1971),
Vol.
Solar
6, pp. 22-24.
Economic Balance Utilizing
Powered Refrigerator,
Sheet of Ice Manufacture
the Sun as the Heat
4, U.N. Publication
Sales No.
Source, 63.1.38,
- 67 APPENDIX A Charging For this sometim es into
a solution
more economical
water
under
not require
developed
of ammonia in water
to buy anhydrous
controlled
Since
strength. did
research,
conditions
the solar-powered
periodic
a leaks
a solution
refrigerator
the ammonia was bled
it
off
of the
was required for
is
directly desired
was a closed-system ,
Recharging
recharging.
or if
ammonia and unload
to obtain
It
was required.
if
it the unit
any reason.
Equipment 1.
Liquid
ammonia cylinder
2.
Demineralized
water
3.
Aqua-ammonia
reservoir
4.
Pressure
5.
Rubber hose
6.
Potassium
7.
Weighing
8.
Valves
9.
Vacuum pump.
tank
gauge
dichromate scale,
O-200 lbs
Procedure Set up the equipment
as shown in Figs.
to remove air
from the system.
of the system.
Therefore,
It
fs advisable
the demineralized refrigeration
The presence
system.
and A2. of air
It
impairs
is
necessary
the performance
a vacuum pump is required.
to add potassium water
Al,
to minim ize
dichromate internal
(1 ounce per 60 pounds)
corrosion
of the
solar-
to
- 68 The following
a)
Open V-6,
V-l,
PumPS then
b) C)
steps
V-3 to evacuate
all
air
reservoir.
Open V-l,
18,9
V-2 and V-5 to let close
Allow
the
reservoir
to cool
will
f)
Evacuate
solar
Ed
Remove the aqua-ammonia
fall
To get charging the vapour
flow
pressure
pressure
in
watering
and the
The charging full.
pounds of water
into
the
aqua-ammonia
pounds
of
liquid
then
close
V-3 and V-4.
for
about
six
&dnia
or eight
refrigeration
reservoir
unit
hours
after
which
by a vacuum pump.
from the mixing
unit
as shown in Fig.
A3.
from
the aqua-ammonia
reservoir
in the
the generator. reservoir
process
16.1
to a low level.
powered
to the refrigeration
is half
to let
the reservoir,
the
from the system by a vacuum
V-5 and V-2.
Open V-3 and V-4 gently into
procedure:
valves.
the pressure
h)
in the charging
Weigh the empty aqua-ammonia
slowly
e>
V-2,
close
reservoir;
d)
are taken
is
reservoir Therefore is heated
stopped
equipment
must be higher
to the than
the generator by the
is
and fit
it
generator,
the vapm cooled
by
sun.
when the upper
header
of
the generator
Demineralized later
Tank
a”
Aqua
-
Ammonia v-2
Reservoir
L Rubber
V-6
HOSI?
Fig. Al
-
Mixing
Equipment
70
Fig. A2 - Mixing
Equipment
- 71 -
- 72 APPENDIX B Estimation It
of is
Incident
Solar
assumed that
the
-2 -1 Cal cm day , inclined half
plane
We shall
radiation
function
of inclination
radiation
200 -+oo Daily
= totals
were recorded
global
using
engineering During
of the angle
of the
faced
the vertical
multiplied
by the factor
radiation Since
normally global
radiation
Actinograph
(D')
is
on the roof
are shown in Fig.
the sun passed very
was inclined
at an angle
of direct in order
solar
of 20'
to estimate
the
Bl.
to the zenith
that,
radiation
(Q)
= collector
direct
radiation
since
the
to the should
be
component
GE direct
+ diffuse
radiation,
(Q')
178 + (Q-200) global
close
of the
on the collector,
on the inclined
daily
to be
of Technology
installed
D' + (Q-200)
where Q is the
Therefore,
estimated
Institute
The results
tests
cos 20'
radiation
and is one
to the horizontal.
at the Asian
component
incident
on an
of inclination
assumed as an approximation
south)
horizontal,
radiation
vertical.
collector
of AIT.
was therefore
(which
is
is 200
emB2 day-l,
radiation
building
It
inclined
a Bimetallic
the period
at midday. collector
178 cal
the diffuse
= 20 degrees
on the
in May in Bangkok
assume that
of the maximum amount when the plane
the diffuse
total
diffuse also
is a linear
The angle
north
Radiation
radiation.
cos 20" x 0.94
cal
-2 -1 cm day ,
55C i
500
‘;;
45c , 4oc
..g 35c $3OC 2 25C 200
100
Fig. 01 -
-- ----Doily Institute
-Global of
May 1975----
S&or
-----
Radiation
Technology
___-
at
The
_ .__ ._
Asian
