FUNDAMENTALS OF THERMODYNAMICS
10th Edition
ISBN: 9781119634928
Author: Borgnakke
Publisher: WILEY
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provide solutions using the ASHRAE tables and chartsAnswer only the d, e and f
5. A refrigerator with tetrafluoroethane as refrigerant operates with an evaporation
temperature of 247.15 K (-26°C) and a condensation temperature of 300.15 K
(27°C). Saturated liquid refrigerant from the condenser flows through an expansion
valve into the evaporator, from which it emerges as saturated vapor.
(a) For a cooling rate of 5.275 kW, what is the circulation rate of the refrigerant?
(b) By how much would the circulation rate be reduced if the throttle valve were
replaced by a turbine in which the refrigerant expands isentropically?
(c) Suppose the cycle of (a) is modified by the inclusion of a countercurrent heat
exchanger between the condenser and the throttle valve in which heat is transferred
to vapor returning from the evaporator. If liquid from the condenser enters the
exchanger at 300.15 K (27°C) and if vapor from the evaporator enters the
exchanger at 247.15 K (-26°C) and leaves at 294.15 K (21°C), what is the
circulation rate of the refrigerant?
Additional Instructions: Define each enthalpy obtained from tables and chart and draw the p-h
diagram labeling the respective evaporating and condensing pressures and
temperatures in each problem.
(2) A standard vapor compression system produces 20 tons
of refrigeration using R-12 as a refrigerant while operating
between a condenser temperature of 41.6 C and an evaporator
temperature of -25°C. Determine (a) the refrigerating effect in
kJ/kg, (b) the circulating rate in kg/s, (c) the power supplied,
(d) the COP, (e) the heat rejected in kW, and (f the volume flow
rate in L/s.
Ans. (a) 100.26 kJ/kg, (b) 0.7022 kg/s, (c) 25.69 kW,
(d) 2.74, (e) 96.09 kW, (f) 92.18 L/s
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- A two-stage refrigeration system operates with ammonia refrigerant flowing at the rate of 15 kg/min through the evaporator. The saturation temperature in the condenser and evaporator units have been noted to be 40⁰C and - 15⁰C respectively. If the system has intercooling by liquid refrigerant at 4.25 bar, determine (a) The capacity and COP of the system. (b) How will these parameters be affected if the compression is carried out in a single stage unit ; the operating temperature limits remaining the same? Use the p-h chart and property tables for saturated ammonia refrigerantarrow_forwarda. Sketch the process on a P-V diagram b. Determine the rate of heat transfer from Boiler ( Qcv/m 1-2, in KJ/kg) c. Determine the rate of heat transfer from condenser ( Qcv/m 3-4, in KJ/Kg) d. Using the Clausius inequality to determine if the cycle is internally reversible, irreversible, or impossible. e. Determine the thermal efficiency of power cycle f. Determine the maximum thermal efficiency of power cycle ( Carnot Efficiency) g. Due to part (e & g) this cycle is___________ ? - internally reversible -internally irreversible -impossiblearrow_forwardRefrigeration system Reminder: Present step by step solution. If EB in to be used, start in System Under Study, then, Fluid Under Study, and draw BED.arrow_forward
- What are the four processes that make up the simple ideal vapor compression refrigeration (VCR) cycle? Make sure you mention what is physically happening during each process Themodynamics question. please explain briefly.Thank youarrow_forwardA heat engine using 120mg of helium as the working substance follows the cycle shown in the following figure. a. Determine the pressure, temperature, and volume of the gas at point 1, 2, and 3. b. What is the W, Q and DEint for each process 1->2, 2->3, and 3->1?arrow_forwardThe condensing and evaporating pressures in a 10 TR refrigeration system are 11.82 bar and 1.64 bar, respectively. The refrigerant enters the compressor at dry and saturated state and leaves the condenser subcooled by 10°C. The actual COP is 70% of its theoretical value. Determine: a. The theoretical COP b. The actual COParrow_forward
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- ! Required information Problem 08.048 - DEPENDENT MULTI-PART PROBLEM - ASSIGN ALL PARTS - Piston Device with Refrigerant NOTE: This is a multi-part question. Once an answer is submitted, you will be unable to return to this part. A piston-cylinder device initially contains 2 kg of refrigerant-134a at 100 kPa and 20°C. Heat is now transferred to the refrigerant from a source at 150°C, and the piston, which is resting on a set of stops, starts moving when the pressure inside reaches 120 kPa. Heat transfer continues until the temperature reaches 80°C. Assume the surroundings to be at 25°C and 100 kPa. R-134a 100 kPa 20°C 150°C Problem 08.048.d - Efficiency of Piston Device with Refrigerant Determine the second-law efficiency of this process. The second-law efficiency of this process is %.arrow_forward! Required information Problem 08.048 - DEPENDENT MULTI-PART PROBLEM - ASSIGN ALL PARTS - Piston Device with Refrigerant NOTE: This is a multi-part question. Once an answer is submitted, you will be unable to return to this part. A piston-cylinder device initially contains 2 kg of refrigerant-134a at 100 kPa and 20°C. Heat is now transferred to the refrigerant from a source at 150°C, and the piston, which is resting on a set of stops, starts moving when the pressure inside reaches 120 kPa. Heat transfer continues until the temperature reaches 80°C. Assume the surroundings to be at 25°C and 100 kPa. R-134a 100 kPa 20°C Q 150°C Problem 08.048.a - Work Done by a Piston Device with Refrigerant The work done is Determine the work done. Use the tables for R-134a. (You must provide an answer before moving on to the next part.) | kJ.arrow_forward! Required information Problem 08.048 - DEPENDENT MULTI-PART PROBLEM - ASSIGN ALL PARTS - Piston Device with Refrigerant NOTE: This is a multi-part question. Once an answer is submitted, you will be unable to return to this part. A piston-cylinder device initially contains 2 kg of refrigerant-134a at 100 kPa and 20°C. Heat is now transferred to the refrigerant from a source at 150°C, and the piston, which is resting on a set of stops, starts moving when the pressure inside reaches 120 kPa. Heat transfer continues until the temperature reaches 80°C. Assume the surroundings to be at 25°C and 100 kPa. R-134a 100 kPa 20°C Q 150°C Problem 08.048.c - Exergy Destroyed by Piston Device with Refrigerant Determine the exergy destroyed. (You must provide an answer before moving on to the next part.) The exergy destroyed is kJ.arrow_forward
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