PHE Evaporator

[Rajkumar]

Can we use Dx type PHE Evaporator for chilling water.

[Rajkumar]

Can we use Ammonia Dx PHE?

Raj

[PaulZ]

Hi Rajkumar
Yes you can.
I have seen them on ***** systems.
They had mechanical or electronic type TX valve fitted.
I haven't seen the NH3 one using at TX but have seen PHE connected to a pumped liquid system using a hand expansion valve instead of the TX.
There was a recent post about this and I think it was sated thad the PHE has to be constructed to suit a TX valve.
Paul

[Rajkumar]

I have seen it in Mycom screw package catalouge

[S.M.Gokhale]

Rajkumar,
There have been large scale failures when PHEs were used in India for chilled water application - reason being water containing dirt and dust clogs the very narrow passages resulting in low chilled water flow which leads to freezing of water in the PHE.
And as the brazed PHE can't be repaired you just have to throw it away. Carrier Aircon had introduced compact chiller using PHEs as condenser and chiller and used to advertise it as a 40 Ton chiller on castor wheels which you can easily transport through an ordinary lift. The product was withdrawn from the market.

A handful of installations using PHE as chiller have been successful. Some tips - use GI piping and elbows, instal an evaporator pressure regulating valve to ensure the evaporation pressure does not go below 27 Deg. F and maintain a clean system.

Also flooded PHEs can be used for ammonia as DX ammonia system can be very tricky (oil return problems).

[PaulZ]

Hi S.M. Gokhale
We have installed many PHE chilling either water or brine and have had no major problems with PHE's failing due to freeze up as all PHE's have a flow switch and an anti-freeze thermostat fitted. We also run the pump on for about 5 minutes after the call is lost.
An EPR valve is also a good idea if you are running other lower temp evaporators on the same system.
I presume by GI you mean galvanized iron pipe, if so I would not recommend the use of GI pipe, as the internal galvanizing can be destroyed by electrolysis and will rust from the inside out. This rust will also end up in the PHE and block it.
We would only stainless steel, copper or PVC.
Also S/S PHE's are susceptible to damage from high levels of Chlorides in the chilled solution.
Paul

[chemi-cool]

PHE are the most common in laser cutting machines, used to cool the water for laser lamps,
I maintain two factories and we don't have any problems except a probe that went crazy and the PHE froze and had to be replaced.

For maximum protection, a HGBP can be fitted to protect it from freezing, make sure that probes, flow controls and the low pressure stat are checked on regular bases.