Binder6 - Assignment 6 2nd Law Heat Engine Refrigerator D36...

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Unformatted text preview: Assignment 6 2nd Law, Heat Engine, Refrigerator D36 A steam power plant with a power output of 150 MW consumes coal at a rate of 60 tons/h. If the heating value of the coal is 30,000 kJ/kg, determine the thermal efficiency of this plant. Answer: 30.0 percent , D37An automobile engine consumes fuel at a rate of 28 L/h and delivers 60 kW of power to the Wheels. If the fuel has a heating value of 44,000 kJ/kg and a density of 0.8 g/cm3, determine efficiency of this engine. Answer: 21.9 percent D38A household refrigerator with a COP of 1.5 removes heat fi'om the refrigerated space at a rate of 60 kJ/min. Determine (a) the electric power consumed by the refrigerator and (b) the rate of heat transfer to the kitchen air. Answer: (a) 0.67 kW, (b) 100 kJ/min D39An air conditioner removes heat steadily from a house at a rate of 750 kJ/min while drawing electric power at a rate of 6 kW. Determine (a) the COP of this air conditioner and (b) the rate of heat transfer to the outside air. Answer: (a) 2.08, (b) 1110 kJ/min D40A Carnot heat engine receives 650 M of heat from a source of unknown temperature and rejects 200 kJ of it to a sink at 17°C. Determine (a) the temperature of the source and (b) the thermal efficiency of the heat engine. Answer: (a) 942.5 K‘ (b) 0.69 D41An inventor claims to have developed a heat engine that receives 750 kJ of heat from a source at 400 K and produces 250 kJ of net work while rejecting the waste heat to a sink at 300 K. Is this a reasonable claim? Why? Answer: No. Actual efficiency is higher than Carnot efficiency. D42An air-conditioning system is used to maintain a house at 75°F when the temperature outside is 95°F. The house is gaining heat through the walls and the windows at a rate of 750 Btu/min, and the heat generation rate within the house from people, lights, and appliances amounts to 150 Btu/min. Determine the minimum power input required for this air—conditioning system. Answer: 0.79 hp D43A heat pump is used to heat a house and maintain it at 24°C. On a winter day when the outdoor air temperature is -5°C, the house is estimated to lose heat at a rate of 80,000 kJ/h. Determine the minimum power required to operate this heat pump. Answer: 2.17 kW E . . 51:3 College of Engmeermg m UNIVERSITY 9! ARKANSAS (Biz/9% 5784241 firm", F/Qfl7‘ WW : AfiZ/VIW CtA/ £54957 £5 fi’M/[f‘ AMA, 44m 30} (9624 Arr/,6, Ffmy [7,44 5474 J” 2 W .. 6;” 3% am 4? 45 72% 9&7, 2,, Mr 49 51}; X '77:” 7* //7fw< ”(zaagg—X /&m37 7/5 W ///\ k/ ’7 fl 157‘?» 3 274—. 7f3.( a 33 a College of Engineering UNIVERSITY W 49(72maéayz' Pig/0L fly mg; 231/4, A/Mf = 63 I“! #[email protected] WM flaw @745 J”: éffi/dm” % College of Engineering UNIVERSITY 9‘ ARKANSAS W fi‘jfimvv'fpw (AR) Cé’f” : /, 5' L QM r 60 1:? ,zn Q /m M w FIND 7‘ fit” (WM POW“ Cfihé‘UwM. ~31 (6} W W 50407123,“ 2 Qt. (A) Cora , 77. Mr QL 50/33" _ / Z/g k"? E College of Engineering UNIVERSITY 9/ ARKANSAS Wlillilhl College of Engineering M UNIVERSITY 9/ ARKANSAS sleraI fl (Sam/914 Mrf Fry/r11 % : 4:0 /<:r Lb 6h; 206K? «L4H 7L ; /:7&¢ : z7a/< "—ny College of Engineering Hm...— UNIVERSITY 9! ARKANSAS w - H, E. 4’9 : [7.49/67 7,; :- y/ék 71 :: 3629/< £724? .2} 7%,} mx‘wméé ,7 Sid OZ‘Z'Q 1; ma; érfigw 9’3 ac all .3’ 7;-7; (IL/2:19 N C 739 1“- ym— 3445 Mn 6 W0 (T? J ? 5 5. ZAS‘ I .5. College of Engineering —-—-—-— UNIVERSITY 9" ARKANSAS 7;: —r’c s gag/R 4m: éfl/qfldé kit/X,- E5410 I ”Mai-y, Esta... w 4- ' v «a. “’7’ ‘fi/E q“ @ ’3 #ié‘fl'fl S'flg I ? cam :- flg 79w 5&4 dfl/‘I’fi/a £4 .. 6M3!) :7 «1‘: 4/} r..- 35;,»- Math (—4; {MK W _._- 7"? ,. 3.2.1....) 3 //Z 9/ ”Kg/my 5—7; ' “29’?— 24> ”V /’) I w __ Palace; I?” JR :— x/A " A. :3 /A 24/ 0)" ...
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