R404a water cooled condensing unit with 8oC cooling water

[Peter_1]

I checked selection condition. We always have 10oK superheat (will be set by TXV) : -30oC To(evaporation) + 10 oK superheat = - 20 oC suction gas temp. and -10oC To(evaporation) + 10 oK superheat = 0 oC suction gas temp..
Evaporator also chosen according -10oK superheat

Other Question:
1.In case we have shell and tube condenser, which may act as receiver also. should we have dedicated receiver for my case (r404a with low condensation temp) ?
2. Crankcase heater should be installed with low suction gas like this or not ? Normally we need not have this one in our country ever after long time turn back cause high ambient condition (lowest 8oC- normally 20-25oC) but i'm not sure if compressor and condenser inside room (20-28 oC).

Regards

Don't understand why you subtract twice 10K and uses twice evaporation. When refrigerant is leaving your evaporator, it's all evaporated as a superheated gas.

You evaporate at -30°C, 10 K superheat is too much, 7K, so -23°C leaving evaporator and +/- 10K along suction line = -13°C inlet compressor

Select compressor for -30°C and 20K total SH and your evaporator at -30°C and 7K SH.

1. You don't need a receiver but charge is then somehow critical. You can install one but it isn't necessary.
And you will not see low condensing pressures, the WVFX will maintain a stable HP.
I feel you still doesn't get the whole picture.
Perhaps this will help http://www.danfoss.com/NR/rdonlyres/.../PFD00A102.pdf


2. If you have pump down, no CCH needed. As you said, it's hot enough in your country to omit a CCH. The temperature of the returning gas has nothing to do with the need for a CCH.

[wta12]

Don't understand why you subtract twice 10K and uses twice evaporation. When refrigerant is leaving your evaporator, it's all evaporated as a superheated gas.

You evaporate at -30°C, 10 K superheat is too much, 7K, so -23°C leaving evaporator and +/- 10K along suction line = -13°C inlet compressor

Select compressor for -30°C and 20K total SH and your evaporator at -30°C and 7K SH.

1. You don't need a receiver but charge is then somehow critical. You can install one but it isn't necessary.
And you will not see low condensing pressures, the WVFX will maintain a stable HP.
I feel you still doesn't get the whole picture.
Perhaps this will help http://www.danfoss.com/NR/rdonlyres/.../PFD00A102.pdf


2. If you have pump down, no CCH needed. As you said, it's hot enough in your country to omit a CCH. The temperature of the returning gas has nothing to do with the need for a CCH.

Sorry for my unclear statement. It's water cooled condensing unit for cold and chiller room.
First is for meat and sea food so they have -30 oC evaporation and -23 oC cold room temperature with suction gas temp -20oC for 10oK super heat

Second is a for higher condition (vegetable, beverage,....) so they have -10 oC evaporation and 0oC suction gas temp. (10o SH also) like compressor selection data This for worst case Maybe it's T evaporation will be raised up if have other requirement.

For SH calulation : for +10 oK along suction line as you said, could i avoid it because if suction line exposed to air room, we will have frost. i want to insulated it.

I have no experience with refrigerant line cause nearly all of my work before come with HVAC system so most of refrigeration work come from chiller's manufacture guys. and it's completely different condition with HVAC chiller. May be it's not all but i'm very appreciated your supports.
Thank alot