How do you calculate the discharge temperature of a compressor?
For centrifugal compressor, the delta temperature can be calculated with 2 methods:
- Isentropic method where DT ideal= T1*[r^((k-1)/k)-1] and DT actual= DT ideal / ηis.
- Polytropic method where DT poly= T1*[r^((n-1)/n)-1]
How do you calculate discharge temperature?
The discharge line temperature is measured at the service valve provided on the compressor’s discharge. The thermocouple (Temperature measurement device) is used to measure the temperature of the discharge. The saturated temperature can be obtained by measuring the pressure gauge pressure.
What is a normal temperature for a discharge gas line on a reciprocating compressor?
Gas Composition:
In standard practice, it is advisable to never exceed operating discharge temperatures of 176.7°C (350°F), however, many compressor packages will consist of components limiting discharge temperature to no more than 148.9°C (300°F).
What is discharge temperature of air compressor?
For the health of the air compressor, the temperature at the discharge line should never exceed 225 degrees Fahrenheit. Anything hotter at the discharge line would put the discharge port dangerously above the 300 degrees Fahrenheit level.
How is compressor discharge pressure calculated?
Compression process. Compression ratio (R) – is the pressure ratio at discharge to suction pressure: R = Pd/Ps (where Pd and Ps are absolute). One stage compressor has only one R value.
Why should the temperature inside the compressor be kept under 300 F?
(14.16). The 300°F temperature limit is used for reciprocating compressors because the packing life gets shortened above about 250°F, and the lube oil, being directly involved in the compression process, will degrade faster at higher temperatures.
What is the normal discharge temp?
Copeland compressors state that the discharge temperature should never be over 225 and an average discharge temperature should be around 180 to 200 degrees F. on a normally operating system. By adding this diagnostic measurement to your “arsenal” of diagnostics, you can really see what is going on with a system.
What is the formula for calculating discharge superheat?
Dear Trane2york, Answer #1: Discharge Superheat = Temperature of discharge line 6” downstream of the compressor discharge service valve (semi-hermetic) or discharge connection (hermetic) – saturated temperature of the liquid line (obtained from P/T conversion of liquid line pressure).
How hot should compressor discharge line be?
It is desirable to limit discharge temperatures to below 250°F to 275°F (121°C to 135°C) to assure adequate packing life and to avoid lube oil degradation.
What is the maximum compressor discharge temperature?
The limit to any compressor discharge temperature is 225 degrees F. If the discharge temperature gets higher than 225 degrees, the system may start to fail from worn rings, acid formations, and oil breakdown.
What does high discharge temperature mean?
High discharge temperature is the result of temperatures in the compressor head and cylinders becoming so hot that the oil loses its ability to lubricate properly. This causes rings, pistons and cylinders to wear resulting in blow by, leaking valves, and metal debris in the oil.
What is discharge line temp?
The compressor’s discharge line temperature can be measured by placing an insulated thermistor on the discharge line about 3 inches from the compressor. This discharge line temperature is a measure of the superheated refrigerant’s vapor temperature.
Why does compressor discharge temperature high?
What causes high discharge temperature? High discharge temperature is the result of temperatures in the compressor head and cylinders becoming so hot that the oil loses its ability to lubricate properly. This causes rings, pistons and cylinders to wear resulting in blow by, leaking valves, and metal debris in the oil.
What causes low discharge temp?
Low discharge superheat usually the situation occurs because of overcharge of refrigerant or overcharge of oil. Both condition gives lower discharge temperature. Once the refrigerant is saturated with oil low discharge will continue to occur.
How do I know if my compressor discharge superheat?
The compressor’s discharge temperature can be measured by placing an insulated thermistor or thermocouple on the discharge line about 3 to 4 inches from the compressor. The discharge temperature is a measure of the superheated refrigerant’s vapor temperature.
Why is the compressor discharge line hot?
How is compressor discharge superheat calculated?
The discharge superheat is calculated the same way as any other superheat/ subcool on a system. By measuring the discharge superheat you can subtract the suction superheat and that then leaves you with a figure of how much superheat the compressor has given through compression and mechanical /electrical inefficiencies.
What causes high discharge temp?
How do you calculate superheat temperature?
The total superheat calculation is as follows: Degrees compressor in temperature (50 degrees) minus saturation temperature (23 degrees) equals total superheat (27 degrees). In the above example, the total superheat was calculated to be 27 degrees.
What is the superheat formula?
How do you calculate subcooling and superheat?
Subtract the Liquid line Temperature from the Liquid Saturation Temperature and you get a Subcooling of 15. “Typically” on TXV systems the Superheat will range between 8 to 28 degrees with a target of about 10 to 15 degrees. The Subcool range on TXV systems will range from about 8 to 20.
What is the formula for subcooling?
Calculate the subcooling as follows: subcooling = CT – T. For a refrigerant blend use the saturated liquid (bubble) temperature as the condensing temperature. Subcooling will not usually occur in the condenser unless liquid backs up in the condenser.
What is the formula for target superheat?
Target Superheat Formula: Indoor wet bulb times 3,minus 80, minus outdoor dry bulb, divide by two.
What is the standard superheat?
approximately 10F
Superheat for most systems should be approximately 10F measured at the evaporator; 20°F to 25°F near the compressor. If the suction pressure is 45 psi, (which converts to 22°F) and the suction temp is 32°F, the system still has 10°F of superheat.
What happens if superheat is low?
A low or zero superheat reading indicates that the refrigerant did not pick up enough heat in the evaporator to completely boil into a vapor. Liquid refrigerant drawn into the compressor typically causes slugging, which can damage the compressor valves and/or internal mechanical components.