7. A single stage air compressor handles 0.5 cubic meter per sec of atmospheric air at 27 O C and delivers it to a receiver at 655 Kpa. Its volumetric efficiency is 0.75, its compression efficiency is 0.90 and its mechanical efficiency is 0.9. If it rotates at 400 rpm, calculate the power required to drive if a) compression is isentropic. b) compression is isothermal

7. A single stage air compressor handles 0.5 cubic meter per sec of atmospheric air at 27 O C and delivers it to a receiver at 655 Kpa. Its volumetric efficiency is 0.75, its compression efficiency is 0.90 and its mechanical efficiency is 0.9. If it rotates at 400 rpm, calculate the power required to drive if a) compression is isentropic. b) compression is isothermal

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

Chapter40: Typical Operating Conditions

Section: Chapter Questions

Problem 10RQ: The seasonal energy efficiency ratio (SEER) includes the energy used in the _____and _____cycles.

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(a) What would be the necessary bore and stroke of a single acting four- cylinder, 350 rpm ammonia compressor working on simple saturation cycle between 35°C condenser and -15°C evaporator temperatures and developing 15 tons refrigeration. Given for the compressor: Ratio of stroke to bore = 1 Volumetric efficiency = 0.7 (b) If the index of compression is 1.15, find the error introduced in calculat- ing the work of compression by assuming the process to be isentropic. Also, find the heat rejected to the compressor-jacket cooling water.
1) A singe acting, twin cylinder, ammonia compressor with bore equal to stroke is driven by an engine at 250 rpm. The machine is installed in a chilling plant to generate 700 kW of refrigeration at -18C evaporating temperature. At this temperature, the cooling effect per kg mass is 1160 kJ. The sp volume of vapor entering the compressor is 0.592 m³/kg. Assume 85% volumetric efficiency. Calculate the bore in mm.
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3.11) The conditions of air at the entry of an axial compressor stage are: Рi %3D 768 тт Hg & Ti = 314 K. The air angles are B1 = 51°, B2 = 9°, a1 = az = 7°. The mean diameter 50 ст. The peripheral speed 100 m/s. Mass-flow rate 25 kg/s work done factor 0.95 mechanical efficiency 92 % stage efficiency 88 % (a) Air angle at the stator entry, [a2 50.18°] (b) Blade height at entry and the hub-tip diameter ratio, [h, = 19 cm ; dn/d = 0.449] (c) Stage loading coefficient. [V = 0.754] (d) Stage pressure ratio. [Po3/Po1 1.075] (e) The power required to drive the stage. [Power = 204.75 kW]
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28. A centrifugal air compressor compresses 200 cfm from 12 psia to 90 psia. The initial specifie volume is 12.6 and final specific volume is 3.25 If the inlet suction lirfe is 4" I.D. and the discharge line is 2.5" I.D. Determine ft-lb (a.) The change in flow energy between the boundaries in- min Ib (b.) the mass flow rate in and min (c.) the change in velocity in fps.
Gas Compressors 14.5 Find the cylinder dimension of a single-cylin der, double acting compressor handling 28.32 Its/revolution of air from 99.975 Kpaa to 723.954 kPaa. Compression and reexpansion are in accordance with p35 = C. Use the conventional volumetric efficiency; c = 5% and L/D =1. Ans. 26.77 x 26.77cm
The compression ratio of an Otto cycle is 8, at the beginning of the zanthropic compression process, the pressure of the air is 100 kPa, the temperature is 27 "C, the volume is 550 cm. At the end of the lzantropic expansion process, the temperature of the air is 700 K. Using the specific temperature values at room temperature (according to the cold air standard assumptions) Find the gravity of the air.
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Exampie Air conditioning unit uses Freon R-22 for conditioned office at 25 C. The evaporating temperature is 17 C and the condensing temperature is 47 C. The compressor is reciprocating and single acting with number of cylinders of 4, volumetric efficiency of 0.9, number of revolution is 900 rpm cylinder dimensions of L/D is 1.25. If the compressor power is 3 kW and mechanical efficiency of 0.9, estimate the followings: the refrigerant mass flow rate in kg/min, refrigeration capacity in TR, cylinder dimensions, condenser heat load, coefficient of performance and relative efficiency. and