‫بسم هللا الرحمن الرحيم‬
Q4: An electric resistance heater is doing work on carbon dioxide contained in rigid tank. FIND
the final temperature in the tank, the amount of heat transfer, and the entropy generation. Assumptions No KE&PE.
2 CO2 ideal gas. Properties The properties of CO2 at an anticipated average temperature of 350 K are
R = 0.1889 kPa.m3 /kg.K, cp = 0.895 kJ/kg.K, cv = 0.706 kJ/kg.K (Table A-2b). Analysis (a) The mass and the final temperature of CO2 may be
determined from ideal gas equation. (b) The amount of heat transfer may be determined from an energy balance on the system: Qout=Ee*change of time-mcv(T1-T2) S generat
Q5 A refrigeration system is to cool eggs by chilled air at a rate of 10,000 eggs per hour.
FIND The rate of heat removal from the eggs, the required volume flow rate of air, and the size of the compressor of the refrigeration system needed.
Make needed assumptions! Properties The properties of the eggs are given to ρ = 67.4 lbm/ft3 and Cp = 0.80 Btu/lbm.°F.
Cp air=
0.24 Btu/lbm. °F (Table A-2E). The gas constant of air is R = 0.3704 psia.ft3 /lbm.R (Table A-1E). Analysis (a) mass flow rate of eggs(10,000 eggs/h)(0.14 lbm/egg) 1400 lbm
Q3:
i) Name ( with sketches for process description and on Property diagrams (T-s) ) all changes/innovations/ that make refrigeration systems more efficient?
ii) Name and ketch other refrigeration systems/cycles other than Vapor Compression Refrigeration! ( 2 sketches: one for the process and one on property (T-s) diagram for the cycle)
iii) A refrigerator operates on vapor compression refrigeration cycle with R-134a as the working fluid. The refrigerant enters the compressor as saturated vapor at 160 kPa, and exits
Q6: An inventor claims to have developed a heat engine. The inventor reports the source temperature TH=500 K The sink Temp TC=290 K. The source heat load QH= 700 kJ. The work output to be W= 300 kJ and QH,
Q7; i) Write down in detail (using drawings,tables, equations and numbers) the differences between a Gasoline Engine and a Diesel Engine!
Q2 i) Air pressure in a tank is measured by an oil manometer. For a given oil-level difference h=0.6 m
between the two columns, Find the absolute pressure in the tank! P atm = 98 kPa Properties: ρoil =
850 kg/m3.
Analysis The absolute pressure in the tank is determined from P =Patm+ ρgh
ii) A cylinder equipped with stops for the piston to rest on is initially filled with saturated water
vapor at a specified pressure. Heat is transferred to water until the volume doubles from0.8--1.6 m3). Find final temp, T3 and the boundary work done by the steam, W, and the amount
of heat transfer Q,
Assumptions: 1 cylinder is stationary KE=PE=0 2 Only boundary work. Analysis: cylinder
contents is the system. closed system since no mass enters or leaves. energy balance for