Reciprocating compressors temperatures

Refrigeration capacity and power P curves for the reciprocating compressor are shown in Fig. 11-92. They are functions of temperatures of evaporation and condensation ... 

If Equation 3.12 is borrowed from the reciprocating compressor chapter and used for an uncooled section, the pressure ratio per section may be calculated assuming an approximate equal-work division. For the first trial, assume the limit of temperature may be achieved in two sections. 

Non-lubricated screw compressors have very close clearances and thus they are designed for limited ranges of discharge temperature, temperature rise, compression ratio, etc., all of which can cause changes in thesc clearances. Lubricated compressors have a somewhat broader tolerance to changes in operating conditions, but they are still more limited than reciprocating compressors. 

The recommendations of the International Standards Organization (ISO) covering mineral-oil lubricants for reciprocating compressors are set out in ISO DP 6521, under the ISO-L-DAA and ISO-L-DAB classifications. These cover applications wherever air-discharge temperature are, respectively, below and above 160°C (329°F). For mineral-oil lubricants used in oil-flooded rotary-screw compressors the classifications ISO-L-DAG and DAH cover applications where temperatures are, respectively, below 100°C (212°F) and in the 100-110°C range. For more severe applications, where synthetic lubricants might be used, the ISO-L-DAC and DAJ specifications cover both reciprocating and oil-flooded rotary-screw requirements. 

H. Roberts (South African Coal, Oil, and Gas Corp.) May I say that for the pilot plant we used a reciprocating compressor which would operate only at near ambient temperature. So we simulated the operation of the hot recycle compressor by adding high pressure steam on the delivery side of the reciprocating compressor. We did not use a hot recycle compressor in the pilot plant. 

Estimate the work required to compress ethylene to 25 MPa in a two-stage compressor. A reciprocating compressor will be used. The gas is at an initial temperature of 15°C and is cooled to 25°C after the first-stage compression. 

So far, we have limited our discussion to adiabatic compression efficiency. This sort of inefficiency downgrades work to heat. For a given compression ratio, the temperature rise of the gas as it flows through the compressor may be excessive, thus indicating a low adiabatic compression efficiency. Both centrifugal and reciprocating compressors suffer from this common problem, which is the subject of Chap. 30. 

CFC-12 was commonly used in domestic and mobile air-conditioning. It normally achieved temperatures down to 20°C, and was suitable for use with centrifugal, rotary, and reciprocating compressors. CFC-11 was used in industrial chillers and other units when a temperature of 5-10°C was adequate. For applications where colder temperatures are required, azeotropic blends involving CFC-115 (CF3CF2CI) and HCFC-22 (CHCIF2) are employed. 

Reciprocating piston compressors. Compression ratios are 1.2 to 6 select to keep outlet temperature <150°C. Efficiencies for reciprocating compressors are 65% for compression ratio 1.5 75% compression ratio 2, and 80% to 85% for compression ratios 3 to 6. Power 70 to 1200 kW/mVs. 

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