Sample Midterm with Solutions-Fall 2022-MECH3201

Q2/ A vapor-compression refrigeration system operates on the cycle. The refrigerant is tetrafluoroethane. For Evaporation T = 0°C; condensation T = 26°C; n(compressor) = 0.79; refrigeration rate = 600 kJ-s—1., determine the circulation rate of the refrigerant, the heat-transfer rate in the condenser, the power requirement, the coefficient of performance of the cycle

During a fall season a heat pump is operating on a heating mode to maintain a large convention hall at 24°C during which the outside temperature is 5ºC. The system is using R134a as a working fluid. The refrigerant leaves the condenser at 30°C and enters a compressor at -5°C. The refrigerant flow rate is 0.3 kg/s. Assume an ideal VCC to evaluate the system and report the followings: a. Draw the system b. Draw process flow diagram for the cycle c. Draw detail Ts diagram for this cycle d. Heating capacity kJ/hr e. What is the COP of the system? Is actual COP is higher or lower? Explain. f. What is the power required kW and hp? g. What is maximum COP?

5. A refrigeration system using R-12 as refrigerant consists of throe evaporators of capacities 20 TR at – 5°C, 30 TR at 0°C and 10 TR at 5°C. The vapours leaving the three evaporators are dry and saturated. The system is provided with individual compressors and multiple expansion valves. The condenser temperature is 40°C and the liquid refrigerant leaving the condenser is saturatoed. Assuming isentropic compression in each compressor, find (a) the mass of refrigerant flowing through cach evaporator, (b) the power required to drive the system, and (c) the C.O.P. of the system. [Ans. 27.4 kg/min, 42.25 kg/min: 34.12 kg/min; 38.4 kW; 5.56]

1) A vapor compression cycle using Ammonia as refrigerant operates at an evaporating temperature of -5 deg. Centigrade and a condensing temperature of 35 deg. Centigrade. The liquid Ammonia was subcooled before entering the thermostatic expansion valve (TEV) to 30°C and the suction vapor was superheated to 20°C without useful cooling. Determine a) the Coefficient of Performance of the cycle. For 15 TOR determine b) the power required by the compressor c) the heat rejected in the condenser d) volume flow rate at the suction.

Please provide steps an solution.

A reversible refrigerator operates using a Carnot refrigeration cycle. It operates usingr-134a between 140 and 400 kPa. The refrigerant exits the compressor (and enters the condenser) assaturated vapor. It also leaves the condenser as saturated liquid.a. Sketch the P-v and T-s diagram of this cycle. Define the coordinate properties of each state oneach graph.b. Evaluate the specific heat and specific work properties of each (in kJ/kg). Indicate the sense.c. Evaluate the coefficient of performance using the specific heats and works from the previousitem. Did it match with the COPR obtained if you used the operating temperatures?   Solve for states first. Then, show the solution to each of the above required in order.

Data for steady-state operation of a vapor-compression refrigeration cycle with Refrigerant 134a as theworking fluid are given in the table below. State 1 is at the compressor inlet. The cooling capacity (i.e therate at which heat is removed from the cooled space) is 4.6 tons. 1 ton of refrigeration is equivalent to211 kJ/min. Ignoring heat transfer between the compressor and its surroundings, sketch the ?-? diagramof the cycle and determinea) the mass flow rate of the refrigerant, in kg/min.b) the isentropic compressor efficiency.c) the coefficient of performance.State ? (bar) ? (°C) ℎ (kJ/kg) ? (kJ/kg-K)

Type: E 1. A vapor-compression refrigeration cycle uses R-134a as its refrigerant. The R-134a enters the compressor as a saturated liquid at 200 kPa, and exits the condenser as a saturated liquid at 800 kPa. The rate of refrigeration of the cycle is to be 3.0 tons of refrigeration. Determine the coefficient of performance of the device as a refrigerator and the mass flow rate of R-134a needed for (a) an isentropic compressor, and (b) an isentropic compressor efficiency of 0.75.

Solve for me. d.e.f.g.h

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1.) An actual 35 TR refrigerating system operates using R22 refrigerant. Refrigerant enters the evaporator at 264.29 kPa and leaves saturated vapour at 244.83 kPa. Refrigerant enters the compressor at – 10°C. Refrigerant leaves the compressor at condensing pressure of 1400 kPa and 70°C and leaves the condenser at 30°C. Compression process is polytropic with n = 1.23. Draw the p-h diagram of the cycle (labeling the pressures and temperatures in each condition). (b) Define and determine the necessary enthalpies and determine the following: (c) IHP and (d) heat rejected during compression, kW

Select a reasonable pressure for the evaporator and condenser in the following scenarios: A) A refrigerator that operates on the ideal vapor-compression cycle with refrigerant-134a is tomaintain the refrigerated space at −10°C while rejecting heat to the environment at 25°C.Select reasonable pressures for the evaporator and the condenser and explain your choice. B) A heat pump that operates on the ideal vapor compression cycle with refrigerant-134a isused to heat a house and maintain it at 25 °C by using underground water at 15 °C as theheat source. Select reasonable pressures for the evaporator and the condenser and explainyour choice.

Pevap=4 bar, Pcond=20 bar, Qevap=6 kW, p6= 8.9 bar Refrigerant ( ammonia (R717) ) leaves the condenser as saturated liquid and as saturated vapor from the evaporator. Compression process in the compressor is isentropic. A) Based on the simple vapor-compression refrigeration cycle below, determine the compressor power and COP. Condenser 3 Evaporator ### Plot the T-s and P-h diagrams for options A Licensed for single user. © 2009 ASHRAE, Inc. -200 40 200 400 600 800 1000 1200 1400 1600 R-717 1800 2000 2200 2400 40 (ammonia) 20 Reference state: h- 200.0 kg. 1.00 kJjko KI for saturated kquid at OC 350 300 150 P: 100 kgm 80 200 10 20 60 8 120 6 40 10 100 30 4 8 80 20 6. 15 2 4 10 8.0 1 6.0 0.8 0.6 T= 20°C 4.0 1 0.8 3.0 0.4 20 0.6 1.5 0.2 0.4 1.0 0.80 0.1 0.2 0.60 0.08 0.06 0.40 0.1 0.30 0.04 0.08 0.20 0.06 0.15 0.02 8.00 0.04 0.10 840 KJkg K) 0.080 0.02 0.01 -200 8.80 0.060 200 400 600 800 Properties computed with: NIST REFPROP 1000 1200 1400 1600 0.01 2400 1800 2000 version 7.0 2200…