A vapor compression refrigeration cycle uses steam as the working fluid. Steamflows steadily with a mass ow rate of 0.5 kg/s. Saturated vapor at 2.0 o C (State 1) enters an uninsulated compressor and it is compressed to 0.35 bar (State 2). Heat transfer at the rate of 105 kJ/s occurs from the compressor to its surroundings and the heat transfer exactly balances the entropy generation rate so that s2 = s1. The boundary and surrounding temperature of the compressor is measured to be 26.67 o C. Steam exits as saturated liquid at 0.34 bar (State 3) from the condenser. Steam leaving the condenser is then throttled in an expansion valve (State 4) before entering a constant pressure evaporator to complete the thermodynamic cycle. (a) Calculate the power (kJ/s) for the compressor. (b) Determine the isentropic efficiency (%) of the compressor. (c) Calculate the entropy generation for the compressor. (d) Find the coefficient of performance of the refrigeration cycle. (e) Show the cycle on T-s diagram. Label states, indicate appropriate lines of constant pressure, and show property values.

A vapor compression refrigeration cycle uses steam as the working fluid. Steamflows steadily with a mass ow rate of 0.5 kg/s. Saturated vapor at 2.0 o C (State 1) enters an uninsulated compressor and it is compressed to 0.35 bar (State 2). Heat transfer at the rate of 105 kJ/s occurs from the compressor to its surroundings and the heat transfer exactly balances the entropy generation rate so that s2 = s1. The boundary and surrounding temperature of the compressor is measured to be 26.67 o C. Steam exits as saturated liquid at 0.34 bar (State 3) from the condenser. Steam leaving the condenser is then throttled in an expansion valve (State 4) before entering a constant pressure evaporator to complete the thermodynamic cycle. (a) Calculate the power (kJ/s) for the compressor. (b) Determine the isentropic efficiency (%) of the compressor. (c) Calculate the entropy generation for the compressor. (d) Find the coefficient of performance of the refrigeration cycle. (e) Show the cycle on T-s diagram. Label states, indicate appropriate lines of constant pressure, and show property values.

Sustainable Energy

2nd Edition

ISBN:9781337551663

Author:DUNLAP, Richard A.

Publisher:DUNLAP, Richard A.

Chapter17: Energy Conservation

Section: Chapter Questions

Problem 14P

See similar textbooks

Similar questions

One pound of an ideal gas undergoes and isentropic process from 95.3 psig and a volume of 0.6 ft³ to a final volume of 3.6 ft3. If Cp = 0.124 BTU/lbm-°R and Cy = 0.093 BTU/lbm-°R, determine: 1. Final temperature in °F 2. Final pressure in psia 3. Change in enthalpy in BTU 4. Work in BTU
A 9.00-mol sample of H₂ gas is contained in the left side of the container shown below, which has equal volumes on the left and right. The right side is evacuated. When the valve is opened, the gas streams into the right side. H₂ Valve Vacuum (a) What is the entropy change of the gas? J/K (b) Does the temperature of the gas change? Assume the container is so large that the hydrogen behaves as an ideal gas. The temperature decreases. O The temperature increases. The temperature does not change. ✓
:A rigid tank contains 5 kg of saturated vapor steam at 100°C. The steam is cooled to the ambient temperature of 25°C. a) Determine the entropy change of the steam, in KJ/K b) For the steam and its surrounding, determine the total entropy change associated with this process, in KJ/K.
The capillary rise (height) in mm of an ethanol having a viscosity of 0.032 J/m2. The tube has a diameter of 0.1 mm and the density of the fluid is 0.71 g/cm3
During a steady flow process, the pressure of the working substance drops from 200 to 20 psia, the speed increases from 200 to 800 ft/s the internal energy decreases 20 BTU/lb and the specific volume increases from 2 to 10 ft³/lb. No heat transferred. Determine the following: a)AKE in ft-lb;/Ibm b)APE in ft-lb/lbm c)AW: (flow work) ft-lb:/lbm d)AH in BTU e) Net work in hp for 15 lb/min of fluid (use mass flow rate for this item only)
At the start of compression in an air standard Otto cycle with a compression ratio of 10, air is at 100 kPa and 313.15 K. A heat addition of 2800 kJ/kg is made. Calculate the thermal efficiency. For air, use k=1.4
Two spherical vessels of different sizes contain the same gas and are connected by means of a pipe with a valve. Sphere A has a diameter of 5 foot at the given pressure gauge of 50 kgf/cm2. Sphere B contains the same gas at 20 kgf/cm² gauge. The valve is opened and when the properties have been determined, it is found out that the gauge pressure is 36 kgf/cm2. The temperature at the two vessels before and after opening the valve is maintained at 21.1°C. If the barometric pressure is 750 torr and the gas inside the sphere is oxygen, find the following: The volume of sphere A is 113097.33 in3 The pressure of sphere A is 711.43 psia The temperature of sphere A is 529.98 R The pressure at sphere B in psia Temperature at sphere B in F The pressure of the gas when mixed in psia The temperature of the gas when mixed in K The atmospheric pressure in psi The diameter of Sphere B The total mass of the gas after opening the valve
0.05 kg of steam at 1.5 MPa is contained in a rigid vessel of volume of 0.0076 m^3. A. What is the temperature of the steam? B. If the vessel is cooled, at what temperature will the steam be just dry and saturated? C. Cooling is continued until the pressure in the vessel is 1.1 MPa, calculate the amount of vapor at this point. D. Calculate the amount of heat rejected between the initial and the final state. E. Draw the Ts diagram of the whole process.
Calculate the temperature of 0.39 mole of Xenon gas that occupies 9850 millimeters under a pressure of 631 torr.
A closed system undergoes a cycle consisting of two processes. During the first process, which starts at an initial system pressure of 1.00 atm and system temperature of 300K, 60 kJ of heat is transferred from the system while 25 kJ of work is done on the system. At the end of the first process, the system pressure is 0.5 atm. During the second process, 15 kJ of work is done by the system. The temperature and pressure of the surroundings are constant throughout at 300K and one atm, respectively. Determine Q, W, ΔU and ΔH for the cycle.
Question 3 A 2L, 4-stroke, 4-cylinder petrol engine has a power output of 113.9 kW at 5500 rpm and a maximum torque of 235 N-m at 3000 rpm. When the engine is maintained to run at 5500 rpm, the compression ratio and the mechanical efficiency are measured to be 8.9 and 83.2%, respectively. Also, the volumetric efficiency is 93.1 %, and the indicated thermal efficiency is 43.76 %. The intake conditions are at 36.9 °C and 1.00 bar, and the calorific value of the fuel is 44 MJ/kg Determine the Air-Fuel ratio in kg/kgf at 5500 rpm. Use four (4) decimal places in your solution and answer.
Steam enters a turbine at 15bar and 600°C with a rate of 0.371 kg/s. The steam expands to 0.08 bar with quality at 90%. Stray heat transfer and kinetic and potential energy effects are negligible. For operation at steady state, • the volume flowrate at the turbine outlet is m³/s, ⚫the power developed by the turbine is ⚫and the temperature at the turbine exit is kW, °C.