The events of a cascade, split-stage, low temperature refrigerating cycle are as follows; A Freon 12 vapor compression system operates between 0˚F and 100˚F with saturated liquid on the high side of the expansion valve and saturated vapor entering the compressor whose volumetric efficiency is 90 %. An ammonia compression system operates between -60 ˚F and 12 ˚F with saturated liquid entering the expansion valve and saturated vapor entering the compressor whose volumetric efficiency is 88 %. The Freon 12 evaporator serves as the condenser for the ammonia for the ideal cycle and 2 tons of refrigeration. Find a) the displacement of each compressor. b) the total horsepower required for compressor efficiency of 80 %.

The events of a cascade, split-stage, low temperature refrigerating cycle are as follows; A Freon 12 vapor compression system operates between 0˚F and 100˚F with saturated liquid on the high side of the expansion valve and saturated vapor entering the compressor whose volumetric efficiency is 90 %. An ammonia compression system operates between -60 ˚F and 12 ˚F with saturated liquid entering the expansion valve and saturated vapor entering the compressor whose volumetric efficiency is 88 %. The Freon 12 evaporator serves as the condenser for the ammonia for the ideal cycle and 2 tons of refrigeration. Find a) the displacement of each compressor. b) the total horsepower required for compressor efficiency of 80 %.

Refrigeration and Air Conditioning Technology (MindTap Course List)

8th Edition

ISBN:9781305578296

Author:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill Johnson

Publisher:John Tomczyk, Eugene Silberstein, Bill Whitman, Bill Johnson

Chapter28: Special Refrigeration Applications

Section: Chapter Questions

Problem 15RQ: Why is two-stage compression popular for extra-low-temperature refrigeration systems?

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2. THE EVENTS OF A CASCADE, A PLIT-STAGE, LOW-TEMPERATURE REFRIGERATING CYCLE ARE AS FOLLOWS: AN AMMONIA VAPOR COMPRESSION SYSTEM OPERATES BETWEEN - 10C AND 33C WITH SATURATED LIQUID ON THE HIGH SIDE OF THE EXPANSION VALVE AND SATURATED VAPOR ENTERING THE COMPRESOR WHOSE VOLUMETRIC EFFICIENCY IS 89%. A R-11 COMPRESSION SYSTEM OPERATES BETWEEN -25C AND OC WITH SATURATED LIQUID ENTERING THE EXPANSION VALVE AND SATURATED VAPOR ENTERING THE COMPRESSOR WHOSE VOLUMETRIC EFFICIENCY IS 85%. THE AMMONIA EVAPORATOR SERVES AS THE CONDENSER OF THE R-11. FOR THE IDEAL CYCLE AND 10KW OF REFRIGERATION, FIND (a) THE DISPLACEMENT RATE OF EACH COMPRESSOR, AND (b) THE TOTAL ACTUAL POWER REQUIRED FOR COMPRESSION EFFICIENCIES OF 85%.
****PART B ONLY In a standard ideal refrigeration cycle (Fig. 1), the refrigerant 134a enters adiabatically isolated expansion valve as a saturated liquid at a pressure P1 = 1 MPa and leaves the device at a pressure P2 = 100kPa. Then the refrigerant enters the evaporator, where it changes into the saturated vapor. Subsequently, the vapor is compressed in an isentropic compressor to the pressure 1MPa and condensed in the condenser back to the initial saturated-liquid state. PART B - To increase the efficiency of the cycle, the expansion valve is replaced by an isentropic turbine.Forthismodifiedcycle,determinetheworkwo′utproducedbytheturbineandthe heat qL′ absorbed by the refrigerant in the evaporator (per 1 kg of the refrigerant).
The events of a cascade, split –stage, low temperature refrigerating cycle are as follows. A Freon 12 vapor compression system operates between 0 F and 100 F with saturated liquid on the high side of the expansion valve and saturated vapour entering the compressor whose volumetric efficiency is 90 %. An ammonia compression system operates between -60 F and 12 F with saturated liquid entering the expansion valve and saturated vapour entering the compressor whose volumetric efficiency is 88 %. The Freon 12 evaporator serves as the condenser for the ammonia for the ideal cycle and 2 tons of refrigeration . Find; a) The displacement of each compressor b) The total horsepower required for compressor efficiency of 80 %
**** PART C ONLY In a standard ideal refrigeration cycle (Fig. 1), the refrigerant 134a enters adiabatically isolated expansion valve as a saturated liquid at a pressure P1 = 1 MPa and leaves the device at a pressure P2 = 100kPa. Then the refrigerant enters the evaporator, where it changes into the saturated vapor. Subsequently, the vapor is compressed in an isentropic compressor to the pressure 1MPa and condensed in the condenser back to the initial saturated-liquid state. USE IMAGE BELOW FOR PART C
The figure shows a two-stage, vapor-compression refrigeration system with two evaporators and a direct contact heat exchanger. Saturated vapor ammonia from evaporator 1 enters compressor 1 at 12 lbf/in² and exits the compressor at 46 lbf/in². Evaporator 2 operates at 46 lbf/in2, with saturated vapor exiting at state 8. The condenser pressure is 200 lbf/in2, and saturated liquid refrigerant exits the condenser. Each compressor stage has an isentropic efficiency of 80%. The refrigeration capacity of each evaporator is shown on the figure. Step 1 -5 Expansion A valve +6 -7 Evaporator Expansion valve Qout Condenser Compressor 2 Qin,2 = 10 tons 8 Evaporator Compressor Direct contact heat exchanger in,1 = 5 tons W₁₂
The figure shows a two-stage, vapor-compression refrigeration system with two evaporators and a direct contact heat exchanger. Saturated vapor ammonia from evaporator 1 enters compressor 1 at 12 lbf/in2 and exits the compressor at 62 lbf/in2. Evaporator 2 operates at 62 lbf/in2, with saturated vapor exiting at state 8. The condenser pressure is 200 lbf/in2, and saturated liquid refrigerant exits the condenser. Each compressor stage has an isentropic efficiency of 80%. The refrigeration capacity of each evaporator is shown on the figure. Determine the temperature, in °F, of the refrigerant in evaporator 2.
A vapour-compression refrigeration system operates with Refrigerant 134 with two evaporators with varying cooling capacity. The low temperature evaporator (#1) operates at -20°C with saturated vapour at its exit and has a refrigeration capacity of 3 tons. The higher temperature evaporator (#2) produces saturated vapour at 3.6 bar at its exit and has a refrigerating capacity of 2 tons. Compression is isentropic to the condenser pressure of 12 bar. There are no pressure drops in the flow through the condenser and the two evaporators and the refrigerant leaves the condenser as saturated liquid at 12 bar. Determine: The mass flow rate of the refrigerant in kg/s through each evaporators;The power input for the compressor, in kW;The coefficient of performance of this refrigeration system;The heat transfer through the condenser in kW;The rates of exergy destruction in each expansion valves in kW for T0 = 300K;Draw the T-s diagram of this system.
A vapor-compression refrigeration system circulates R-134a at a rate (m_dot) of 10 kg/min . The refrigerant enters the compressor at -10 ∘C∘C, 1.2 bar and exits at 7 bar. The isentropic compressor efficiency is 68%. There are no significant pressure drops as the refrigerant flows through the condenser and evaporator. The refrigerant leaves the condenser at 7 bar and 24 ∘C. Ignore the heat transfer between the compressor and its surroundings. (Figure 1) Part A. Determine the coefficient of performance (COPR) Part B. Determine the refrigerating capacity Part C. a. Determine the irreversibility rates of the compressor for an ambient temperature of 20 ∘C b. Determine the irreversibility rates of the expansion valve for an ambient temperature of 20 ∘C
you design a custom refrigeration system using 1,1,2-tetrafluoroethane (R-134a) as refrigerant.You design your ideal compression-based refrigeration cycle to operate between 2 bar and 9 bar. Before enteringthe ideal butterfly valve (delta H = 0), the refrigerant is a saturated liquid. Before entering the compressor, therefrigerant is saturated vapor. In fact, in isentropic operation, the refrigerant which leaves the compressor is alsosaturated vapor. The operation of the compressor and the evaporator is isobaric. Assuming a mass flow rate of1.5 kg / s, determine the compressor efficiency required to achieve a coefficient of performance of 6.96. Whatis ?? ̇ et ?? ̇ to this performance.
A reheat cycle with two stages of reheating is executed with steam expanding initially from 200 bar (20 Mpaa) and 540 deg C. The 2 reheater pressures are 40 bar (4 Mpaa) and 10 bar (1 Mpaa) and the steam leaves each reheater at 540 deg C. Steam is bled in between two reheating sessions at a pressure equal to 20 and 15 bars into 2 open feedwater heaters. Condensation occurs at 60 deg C. All expansion and compression efficiencies are 90 %. There is a total of 10.3 kg/sec of steam (total mass flow rate m) circulated in the cycle. Answer the following: fill up the blanks in the items below: Equipment layout and TS diagram for the cycle. Ideal turbine work (KW) Ans:_______________________________ Actual mass of steam bled into the open heater m1’= _____________kg/sec for the heater nearest to the SGU/boiler and m2’ = _____________________kg/sec for the heater nearest to the condenser. Actual engine efficiency (%) Answer: _______________________ Actual Rankine cycle efficiency %…
A reheat cycle with two stages of reheating is executed with steam expanding initially from 200 bar (20 Mpaa) and 540 deg C. The 2 reheater pressures are 40 bar (4 Mpaa) and 10 bar (1 Mpaa) and the steam leaves each reheater at 540 deg C. Steam is bled in between two reheating sessions at a pressure equal to 20 and 15 bars into 2 open feedwater heaters. Condensation occurs at 60 deg C. All expansion and compression efficiencies are 93 %. There is a total of 4.5+ (3*25/100) kg/sec of steam circulated in the cycle. Answer the following: fill up the blanks in the items below: 1. Equipment layout and TS diagram for the cycle 2. Actual mass of steam bled into the open heater m1'= kg/kg for the _kg/sec for the heater nearest to the SGU/boiler and m2' = heater nearest to the condenser. 3. Actual turbine work in KW Answer: 4. Energy Chargeable (actual) Answer: 5. Ideal Rankine engine efficiency % Answer:
A reheat cycle with two stages of reheating is executed with steam expanding initially from 200 bar (20 Mpaa) and 540 deg C. The 2 reheater pressures are 40 bar (4 Mpaa) and 10 bar (1 Mpaa) and the steam leaves each reheater at 540 deg C. Steam is bled in between two reheating sessions at a pressure equal to 20 and 15 bars into 2 open feedwater heaters. Condensation occurs at 60 deg C. All expansion and compression efficiencies are 90 %. There is a total of 10.3 kg/sec of steam (total mass flow rate m) circulated in the cycle. Answer the following: fill up the blanks in the items below: Actual Rankine cycle efficiency % using Qa’ and Qr’ values Answer: _____________ If the generator efficiency = 95%, brake engine efficiency = 90% what is the plant capacity in MW? Answer: ______________________ If Cp water = 4.187 KJ/kg-K; cooling water enters the condenser at 12 deg C and leaves at 21 deg C, find amount of cooling water needed by the condenser in kg/sec. (ACTUAL) Answer:…