ERT 216 HEAT AND MASS TRANSFER HEAT TRANSFER EQUIPMENT (DRYING) QUIZ
1. Describe Describe the purpose purpose of of drying drying of material material in in processing processing of product. product. Concern with the removal of water from process materials and other substances Example: Drying or dehydration of biological materials (foods) used as preservation techni!ue. ". Compare Compare the the different different between between drying drying and evaporation evaporation.. Drying
Evapra!in
#emo emoval of rela elatively small amount of water of materials
#em #emoval oval of rela relati tive vely ly lar large amounts of water from materials
$ater is removed as vapor by air. %n some cases water may be remo remove ved d mech mechan anica icall lly y by soli solid d materials by presses or centrifuging and other methods
$ater is removed as vapor at its boiling point
Cheaper than drying by thermal
&. 'he 'he air in the room room is at &. &. *C and a tota totall press pressur uree of 1+1. 1+1.& & ,-a abs contai containi ning ng water vapour with a partial pressure of 1+1.& ,-a abs containing water vapour with a partial pressure p/&.0 ,-a. Calculate: a) 2umidity. b) 3aturation humidity and percentage humidity c) -ercen -ercentag tagee relativ relativee humidi humidity ty 4rom the steam tables at &. +C5 the vapor pressure of water is / .& ,-a . lso5 p A / &.0 ,-a and P / / 1+1.& ,-a (16. psia). p AS / 4or part (a)5 using E!. (.&71)
(&.0) +.+"" &.0) (.&) +.+6 .&)
(+.+"")
68.&
+.+6
(&.0)
6.0
.& 6. 'he air entering the dryer has a temperature of 80.8*C and dew point of 10.8*C. 9sing the humidity chart5 determine the actual humidity and percentage humidity.
0. ir enters an adiabatic saturator having a temperature of 8.*C and a dew7point temperature of 6+.8*C. %t leaves the saturator + saturated. $hat are the final values of 2 and ' (*C); Dew point/6+.8*C5 4rom the graph 2/+.+0" and
I"pr!an! Fr"#$a%
