Re: R404a water cooled condensing unit with 8oC cooling water
Where there is refrigerant in both liquid and vapor form (condenser, evaporator), the temperature and pressure coincide.
If the condensing temperature is low, then the condensing pressure is also low. If the condensing pressure is too low then there isn't enough pressure in the condenser to push the liquid refrigerant through the TXV and into the evaporator.
The choices are to raise the temperature of the water or to reduce the flow of water through the condenser. Either of these strategies will raise the condensing temperature/pressure.
The purpose of the water regulating valve is to control the water flow in order to regulate the condensing temperature/pressure.
Re: R404a water cooled condensing unit with 8oC cooling water
Quote:
Originally Posted by
Gary
Where there is refrigerant in both liquid and vapor form (condenser, evaporator), the temperature and pressure coincide.
If the condensing temperature is low, then the condensing pressure is also low. If the condensing pressure is too low then there isn't enough pressure in the condenser to push the liquid refrigerant through the TXV and into the evaporator.
The choices are to raise the temperature of the water or to reduce the flow of water through the condenser. Either of these strategies will raise the condensing temperature/pressure.
The purpose of the water regulating valve is to control the water flow in order to regulate the condensing temperature/pressure.
Thank a lot for a comprehensive conclusion with my situation. How could i check the condensing pressure is enough to push liquid through TXV to select the design condition ?
Regard
Re: R404a water cooled condensing unit with 8oC cooling water
The TXV manufacturer can tell you the minimum pressure drop (difference between high and low side pressures) needed for the TXV to operate properly. It varies with the model/type of TXV.
Re: R404a water cooled condensing unit with 8oC cooling water
As a general rule of thumb, I like to keep a minimum of 30C condensing temperature. This should be enough for all types of TXV's.
Re: R404a water cooled condensing unit with 8oC cooling water
Quote:
Originally Posted by
Gary
The TXV manufacturer can tell you the minimum pressure drop (difference between high and low side pressures) needed for the TXV to operate properly. It varies with the model/type of TXV.
It's seem like i need contact Danfoss (the most popular brand in our country for TEV). I can not find this value in TEV calalogue
Re: R404a water cooled condensing unit with 8oC cooling water
Danfoss TEV's = 2 bar minimum pressure drop but take perhaps 4 bar to have some safety margin. You will have anyhow 9 bar HP with R404a at 15°C condensing and a LP of +/- 3 bar which gives you 6 bar differential
Re: R404a water cooled condensing unit with 8oC cooling water
Quote:
Originally Posted by
Peter_1
Danfoss TEV's = 2 bar minimum pressure drop but take perhaps 4 bar to have some safety margin. You will have anyhow 9 bar HP with R404a at 15°C condensing and a LP of +/- 3 bar which gives you 6 bar differential
Thanks a lot. It's come from your experiences or any source ? i want to verify for model. Ever Danfoss tech. support have not answer for me.
Re: R404a water cooled condensing unit with 8oC cooling water
Both, I have the books here form Danfoss as well. YOu then have bad Danfoss support in your country.
Re: R404a water cooled condensing unit with 8oC cooling water
Could you spend me the soft-copy (pdf) file of this document ?
In case not available, Please let me the name or P/N of document/books, which say about this value.
Thank for your support
Re: R404a water cooled condensing unit with 8oC cooling water
Quote:
Originally Posted by
wta12
The selection software for condenser can choose with Tc =24oC with condenser sub-cooling 1 oK as default of selection software.
This seems a little low to me. Condensers should be sized for worst case scenario. In this case that would be a malfunction of the chiller system and switch to fresh water input. It would seem prudent to oversize the condenser a little (for worst case scenario) and then control the water flow volume (for best case scenario). The overriding question would be, what temperature is the fresh water input?