Assignment on Thermal Engineering

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1. Stud Studen ents ts are are advi advise sed d to refe referr any any of the the refe refere renc ncee text text book bookss to complete the assignments 2. Stud Studen ents ts are are inst instru ruct cted ed to subm submit it the the assi assignm gnmen entt on a both both side side ruled assignment paper ONLY. 3. DUE DATE DATE for the submission of assignment is on 17/05/2015 4. Stud Studeents nts will ill be cal called in a GROUP during the submission of assignments for individual assessment through the VIVA voce 5. NO Credit Credit of marks will be assigned to the students who will found COPYING the assignment during the viva voce. . !ill up your ".#o ".#o and #ame #ame on the $uestion $uestion paper paper and attached attached as a cover page while submitting your assignment.

ASSIGNENT ! DAE "001 T#ERAL ENGINEERING od$%e 1

%asic &oncepts' (eroth law of )hermodynamics and its significance' &oncept of heat and work. *roperties of steam' *roperties of +deal gas. $1.

,n office worker claims that a cup of cold coffee on his table warmed up to -/& by picking up energy from the surrounding air' which is at 25/&. +s there any truth to his claim0 oes this process violate any thermodynamic laws0

$2.

, can of soft drink at room temperature is put into the refrigerator so that it will cool. ould you model the can of soft drink as a closed system or as an open system0 xplain.

$3.

&onsider two closed systems , and %. System , contains 3 k of thermal energy at 2/&' whereas system % contains 2 k of thermal energy at 5/&. #ow the systems are brought into contact with each other. etermine the direction of any heat transfer between the two systems.

$4.

, pressure gage connected to a tank reads 5 k*a at a location where the atmospheric pressure is 4 k*a. etermine the absolute pressure in the tank.

$5.

, room is heated by an iron that is left plugged in.+s this a heat or work interaction0 )ake the entire room' including the iron' as the system.

".#o

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6arks assigned

ASSIGNENT ! DAE "001 T#ERAL ENGINEERING

od$%e 2 & A

!irst law of )hermodynamics' first law of thermodynamics for non flow and steady flow processes. $1.

, gas in a piston7cylinder device is compressed' and as a result its temperature rises. +s this a heat or work interaction0

$2.

8n a hot summer day' a student turns his fan on when he leaves his room in the morning. hen he returns in the evening' will the room be warmer or cooler than the neighboring rooms0 hy0 ,ssume all the doors and windows are kept closed.

$3.

ater is being heated in a closed pan on top of a range while being stirred by a paddle wheel. uring the process' 3 k of heat is transferred to the water' and 5 k of heat is lost to the surrounding air. )he paddle9wheel work amounts to 5 # : m. etermine the final energy of the system if its initial energy is 1 k. Answer: 35.5 k

$4.

, water pump that consumes 2 k of electric power when operating is claimed to take in water from a lake and pump it to a pool whose free surface is 3 m above the free surface of the lake at a rate of 5 ;
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od$%e 2 & '


, fan is to accelerate =uiescent air to a velocity of 1m
$2.

)he driving force for fluid flow is the pressure difference' and a pump operates by raising the pressure of a fluid >by converting the mechanical shaft work to flow energy?. , gasoline pump is measured to consume 5.2 k of electric power when operating. +f the pressure differential between the outlet and inlet of the pump is measured to be 5 k*a and the changes in velocity and elevation are negligible' determine the maximum possible volume flow rate of gasoline.

$3.

, 29k electric resistance heater in a room is turned on and kept on for 3 min. )he amount of energy transferred to the room by the heater is Answer: 3 k

$4.

, 39; electrical radiator containing heating oil is placed in a 59m3 room. %oth the room and the oil in the radiator are initially at 1/&. )he radiator with a rating of 1.- k is now turned on. ,t the same time' heat is lost from the room at an average rate of .35 k
@ Properties )he gas constant of air is R A .2-B k*a.m3
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od$%e 2 & C


, student living in a 49m x 9m x 9m dormitory room turns on her 159 fan before she leaves the room on a summer day' hoping that the room will be cooler when she comes back in the evening. ,ssuming all the doors and windows are tightly closed and disregarding any heat transfer through the walls and the windows' determine the temperature in the room when she comes back 1 h later. Dse specific heat values at room temperature' and assume the room to be at 1 k*a and 15/& in the morning when she leaves. Properties )he gas constant of air is R A .2-B k*a.m3
$2.

, diffuser is an adiabatic device that decreases the kinetic energy of the fluid by slowing it down. hat happens to this lost kinetic energy0

$3.

hat is flow energy0 o fluids at rest possess any flow energy0

$4.

+s heat transfer to or from the fluid desirable as it flows through a noEEle0 Fow will heat transfer affect the fluid velocity at the noEEle exit0 ".#o

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6arks assigned


od$%e (

Second law of )hermodynamics G ntropy H &oncepts of heat engines' refrigerator and heat pump. ntropy' ntropy change for various reversible processes. $1.

,n experimentalist claims to have raised the temperature of a small amount of water to 15/& by transferring heat from high9pressure steam at 12/&. +s this a reasonable claim0 hy0 ,ssume no refrigerator or heat pump is used in the process.

$2.

&onsider the energy generated by a )I set. hat is a suitable choice for a thermal energy reservoir0

$3.

, household refrigerator runs one9fourth of the time and removes heat from the food compartment at an average rate of - k
$4.

, heat pump is used to maintain a house at a constant temperature of 23/&. )he house is losing heat to the outside air through the walls and the windows at a rate of ' k
$5.

, system undergoes a process between two fixed states first in a reversible manner and then in an irreversible manner. !or which case is the entropy change greater0 hy0 ".#o

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Assignment on Thermal Engineering

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