We have a new refrigeration system under commissioning. There are 2 x 63.9 TR compressors Mycom F8WA for R 22 rated at Te -5C and Tc 45 C. The Evaporative condenser is Baltimore VXC125 has a capacity of 140 TR. The expansion valve is PHT 85 from Danfoss and the supplier says it is orifice 4 giving 130 TR. The PHE after the expansion valve is a Thermowave make TL250 designed to run 6821 kg/hr R22 at -5C and water at 30 m3/hr to cool from 14 C to 2 C. There is a chilled water buffer tank 108 m3 capacity.
There observations are as follows:
1. The supplier mentioned about antifreeze upto 25% in water which was not discussed at the order stage. To get over this issue I have asked the system to be commissioned at 4C instead of 2C as stage I. The antifreeze issue will be taken up after the system runs close to its design load.
2. The return water temperature varies from 8-18 C. The Plate heat exchanger gives a steady 3C temperature drop on the chilled water side at 30 m3/hr at all temperature between 8-18C. At this time, one compressor operates at 13 bar on the hp side and 3.6 bar on the lp side. The load % on the control panel varies between 50-75%. This goes to 100% for a few minutes and gets back to 75% even if the water outlet temperature is 6-9 C. The other compressor will not start unless the first runs on 100% capacity.
3. I suspect the expansion valve to be limiting the quantity of the refrigerant. Is there a way to check the performance of this valve? There is a tiny tag at the expansion valve saying orifice no 1. This corresponds to 30TR according to Danfoss catalogue- which is incidentally the capacity delivered by the plant..
My queries are:
1. What will be the change in capacity of the system if we run it at 4C instead of 2C using same equipment?
2. Is there a way to verify the doubt about the expansion valve?
3. If I insist on changing the expansion valve so I get closer to the designed capacity of the plant what are the pitfalls that I must avoid?
Looking for some enlightenment on this matter.:confused:
Regards,
Hemant Anand