Compressor Questions

[MikeAnjin]

Hi all, im new to the forums in terms of posting, but been an avid reader everyday. I have some questions about compressors that i did not see in the sticky section.

I would like to build a SS this summer and i wanted to know how you can calculate the HS and LS pressure for a system.

Im not sure if the compressors are designed to achieve a certain volumetric flow all the time or a certain mass flow. Also how do you calculate the capacity of a system to handle a load?

Im not sure if i am being very clear, but in general i want to know how i design my system around a compressor based on its specs.

Im really hoping one of you here will be able to help or will have some awesome reading material for me. Thanks in advance. Mike

[Clemmaster]

Hi.

Manufacturers give data on their compressors (cooling capacity, power consumption, condensing pressure...). HS and HL are determined by the vaporizing temperature you're aiming. The relation temperature/pressure is given by many program such as Coolpack. The HS must be as low as possible on single stages system with R4xx/R5xx refrigerants (as they always have a >10bar condensing pressure which prevents from high static pressures)

Some manufacturers give a lot of data on their compressors (danfoss for example) and with theses data you can find the volumetric efficiency of theses compressors and then know the massic flowrate with any gases at every commun LS/HS pressures. After you know their volumetric efficiency and the testing conditions you can know in advance their cooling capacity with other refrigerant with a decent accuracy time you stay in normal testing conditions.

[MikeAnjin]

Thank you for your response. i understand some of what you are saying. But how do i know that a compressor will be capable of achieving certain pressures? For example i may know that my refrigerant condenses at 100 psig at 70f. but how do i know that comprossor will reach 100 psig?

[MikeAnjin]

what i want to know is for example, if the refrigerant returns at say 10 psig to the suction line. what will be the Discharge pressure?

[godmod]

To your last question: deends on the charge and refrigerant and restrictiveness and type of metering device as well as displacement of compressor and so on. hard to answer ;)