TECHNOLOGICAL INSTITUTE OF THE PHILIPPINES Thermodynamics Competency Exam NAME!!!!!!!!!!!!!!!!!!!!!!!!!! "ATE#$%#%& "ATE#$%#%& "I'ECTIONS P'O(I"E THE SOLUTION TO SELECT THE )EST ANS*E' 1. A refrigerator operates in a cyclic And reversible manner between 0 and 27ºC. 27ºC. What is the coefficient coefficient of performance performance given that the heat of fusion of water is !.72"#g. a. 101.1$ b. 1011$ c. %0$ d. &'()
2. Air is compressed in a cylinder such that the volume changes from 100 to 10 in. (he initial pressure is %0 psia and the temperature is held constant at 100*+. Calculate the wor,. a. -!! ft-lbf b. !! ft-lbf c. -/%/ ft-lbf d. /%/ ft-lbf . A 1%00-,g automobile automobile traveling at 0 m#s is brought to rest by impacting a shoc, absorber composed of a piston with small holes that moves in a cylinder containing water. water. ow much heat must be removed from the water to return it to its original temperature a. 2% ," b. -1/," c. 7% ," d. / ," !. A refrigerator is rated at a C'3 of !. (he refrigerated space that it cools re4uires a pea, cooling rate of 0000 ,"#h. What si5e electrica6 motor rated in horsepower8 is re4uired for the refrigerator a. 1.1/ 3 b. 1%.2 3 c.2.7/ 3 d. .% 3 %. A heat pump is proposed in which %0*+ groundwater is used to heat a house to 70*+. (he (he groundwater is to e9perience a temperature drop of 12:+; and the house re4uires 7%;000 '2 ? 0.%'2 >' are 1.0 and !./; respectively. Calculate Calculate the average value of @º over the temperature change. a. /!;1!0" b. /!.1!," c. !/;1!0" d. &'() ↔
. +or the ideal Ban,ine c ycle shown in +ig. -2 determine the mass flow rate of steam and the cycle efficiency. efficiency.
10. 3redict the value for the enthalpy of vapori5ation for water at 200*C assuming steam to be an ideal gas. a. %!2 ,"#,g b. 21% ,"#,g c. 1/% ,"#,g d. 27 ,"#,g %%+ Coe,,icient to per,ormance ,or a re-ersed Carnot cyc.e /or0in1 2et/een temperat3res T % and T4 5T%6 T47 is a. (2 #(1 - (28 b. (1 #(1 (28 c. (2 (18 # (1 d. (1 (28 #(2 %4+ One ton o, re,ri1eration capacity is e83i-a.ent to a. %0 %0 , cal#hr b. 20 200 <( <(D#hr c.200<(D#min d.200 <(D#day %9+ In case o, steady ,.o/ compression po.ytropic process 5P(n : constant7; the /or0 done on air is the .o/est; /hen a. n E y E 1.! b. n E 0 c. n E 1 d. n E 1. %<+ As the entropy o, the 3ni-erse is increasin1 day 2y day the /or0 prod3cin1 capacity o, a heat en1ine is a. not changed b. decreasing c. incr increa easi sing ng d. data data insu insuff ffic icie ient nt canF canFtt be be pre predi dict cted ed %&+ F31acity F31acity coe,,icie coe,,icient nt o, a s32sta s32stance nce is the ratio o, its ,31acity to a. mole fraction b. activity c. pressure d. activity coefficient %=+ >o3.e?Thomson experiment is A. isobaric <. adiabatic C. isenthalpic G. bothb8 H c8 %@+ *ater on heatin1 ,rom % to <C A. contracts <. e9pands C. has has same same volu volum me G. may may con contrac tractt or e9pa e9pan nd %B+ %B+ A stea steam m t3r2 t3r2in inee /ith /ith rate rated d capa capaci city ty o, &=;< &=;<## ## 0* 5&=;<# 5&=;<##0> #0>s7 s7 operat operates es /ith /ith steam steam at in.et in.et condit condition ionss o, B;=##0Pa and &##DC; and dischar1es into a condenser at a press3re pre ss3re o, %#0Pa+ %#0Pa+ Ass3min1 a t3r2 t3r2ine ine e,,iciency e,,iciency o, #+@&; determine the mass rate o, ,.o/ o, the steam+ a. !% ,g#s b. !/ ,g#s c. %% ,g#s d. %/ ,g#s %$+ %$+ *hich hich o, the the ,o.. ,o..o/ o/in in1 1 e83a e83ati tion on is o2ta o2tain ined ed on sT nd com2inin1 % and 4 .a/ o, thermodynamics; ,or a system o, constant mass a. dD E (d> 3dI b. dJ E Cv d( ? 3dI c. dJ E Cp d( ? Idp d. (d> E dD 3dI
20. *hich o, the ,o..o/in1 2eha-es most c.ose.y .i0e an idea. 1as A. e <. &2 C. '2 G.2 21. (he reaction is always spontaneous when a. @ is -8@> is ?8 b. @ @ is ?8@> is ?8 c. @ is is ? ?8@> is is -8 d. @ is -8@> is -8 44+ *hich is not a re,ri1erant A. >'2 <. &
C. CCl2+2
G. C2!Cl2
2+ 4+# mo.e o, an idea. 1as is expanded expanded isotherma..y isotherma..y to ,i-e times its initia. -o.3me+ Ca.c3.at ethe chan1e in entropy+ a. 2.0 "#ºC b. %.0 "#ºC c. 2.77 "#ºC d. &'() 2!. Ca.c3.ate the tota. entropy chan1e /hen % mo.e o, ice at #DC is heated to steam at %##DC at #+% MPa press3re+ The mo.ar heat o, ,3sion o, ice at #DC is =+##B 0> and the heat o, -aporiation o, /ater at %##DC is <#+==B 0>+ The speci,ic heat o, /ater is approximate.y <+%B< >DC+1+ a. 22.007 "#ºC.g. b. 22/.!2 "#ºC.g. "#ºC.g. c. !2% "#ºC.g. d. &'() a. 2./ ,g#s; !$ b. 1.1 ,g#s; .%$ .%$ c. 1./$; !2.%$ d. 21./$; 1.7$ 9. An adiabatic compressor receives 20 m#min of air from the atmosphere at 20*C and compresses it to 10 3a. Calculate the minimum power re4uirement. a. 17 ,W b. %! ,W c. !%2=w d. ./0 ,W
2%. Ca.c3.ate the ,ina. temperat3re ,or the com23stion o, a mixt3re o, % mo.e o, hydro1en; #+& mo.e o, oxy1en and 4 mo.e o, nitro1en in a c.osed 2om2 ca.orimeter o, constant -o.3me; 1i-en that the chan1e in entha.py ,or the ,ormation o, % mo.e o, /ater is 4<%+B9& 0> and ,or 1aseo3s H4O and N4; C- o, H4O : 49+B<$ >+mo.e and C- ,or N4 : 4#+B9= >+mo.e+ a. /!.!= b. /!./= c.2%%= d. &'()
