[Cvhesteve]

Hello,
I have an air cooled Smardt chiller (72TR) having issues running high approach fully loaded, 8-10 degrees. It still makes setpoint but obviously not operating optimally. The exv is SEHI-175 which is, if anything, oversized for chiller. It uses about 20% glycol concentration which I understand raises approach slightly. Any advice on areas to verify further would be appreciated

 

[jayguy]

high evaporator approach can be caused by fouling on the refrigerant side (oil, dirt) or on the glycol side (usually dirt) but can also be caused by higher loads, high flow rates, fluid type and concentration.

 

[Healey Nut]

high evaporator approach can be caused by fouling on the refrigerant side (oil, dirt) or on the glycol side (usually dirt) but can also be caused by higher loads, high flow rates, fluid type and concentration.

Low refrigerant charge , faulty temp or pressure sensor , refrigerant level control etc etc etc .

 

[ehsx]

Low refrigerant charge , faulty temp or pressure sensor , refrigerant level control etc etc etc .

Add water box divider plate/gasket, sensor location. Some leaving fluid temp sensors may need to be moved down stream.

 

[milkyway]

What these (3) said

 

[Cvhesteve]

Thank you sir, it’s a Smardt chiller (no oil) and less than 2 yrs old on new install so I would probably rule out dirt/oil issue. However I did notice the piping is undersized. It’s 2.5” supply/return and chiller design flow is 149GPM, I used B&G syzer to estimate velocity around 10fps. The friction loss is extreme around 15ft/100. Could you elaborate for me on how the higher flow velocity impacts approach?

 

[milkyway]

Approach equals saturated versus leaving water temp differential. If you have too much water flow you can’t pick up the heat transfer. If you can slow down the water flow you may see a difference.

 

[Healey Nut]

Approach equals saturated versus leaving water temp differential. If you have too much water flow you can’t pick up the heat transfer. If you can slow down the water flow you may see a difference.

Top of the class Milky , your getting there:grin2::grin2:

 

[jayguy]

Thank you sir, it’s a Smardt chiller (no oil) and less than 2 yrs old on new install so I would probably rule out dirt/oil issue....

i would not rule out dirt (or any debris for that matter) just because it is new. that can sometimes be when it is the dirtiest. installing contractors are not known (as a whole) for cleaning the system up like the manual says they are supposed to do. i know of a brand new screw compressor (that had never been opened) with oil flow problems at start up (we were the start up and factory techs). after awhile, we decided to open up the compressor and change the oil filter...found a candy wrapper in there. you just never know.

...I used B&G syzer to estimate velocity around 10fps. The friction loss is extreme around 15ft/100. Could you elaborate for me on how the higher flow velocity impacts approach?

10 fps is getting up there. like milky said, when the water flow is very high, it isn't in contact with the surface for very long. in order to cool it off before it leaves the heat exchanger, you have to have "colder than normal" refrigerant. also, high flow rates can cause the fluid to move through the heat exchanger in an odd pattern sometimes creating eddy currents (swirls) where the water spins around but doesn't really move through the heat exchanger. this creates a smaller area for the fluid that is moving through the heat exchanger to pass. this means there is a further decrease in the effective heat exchanger surface area.

i would find out what the heat exchangers minimum and maximum flow rates are and make sure you stay within that range if possible. and just because you are within the range doesn't mean that it is the optimal flow rate for the heat exchanger. sometimes salespeople will take the engineers recommended data and "expand" the high and low flow rates to make their product look better than it really is.

 

[Cvhesteve]

Thank you everyone for the feedback, definitely have more to dive into. Appreciate the help

 

[ehsx]

Fluid set point?

 

[Cvhesteve]

44F. Chiller design is 55F ECHW/44F LCHW

 

[nutradesman]

Those use a liquid level sensor in the evaporator, what is the setpoint (they're generally set around 55%)? Is the level sensor reading correctly? What is the EXV percentage at full load? Also bear in mind the approach on these is being calculated off of the compressor suction pressure transducer which tends to be lower than actual evaporator saturation pressure.

 

[Jack 176]

My experience with an air cooled smardt chiller was less than ideal for many reasons,it also would run high approach temp 7-8 , flows were within spec and was running 20% glycol , compressors were constantly faulting and would run low suction pressures. Never got to the bottom of problem, my thoughts were the the chiller barrel didn’t have enough tubes or the tubes weren’t high efficienct tubes. The compressor appeared to be starved for suction gas causing surge /bearing displacement faults. Thing never worked correct and the people who make it and start it up and support it didn’t seem to be very concerned about the performance of they’re machine and it’s end user.

 

[ehsx]

Typically dx evaps have 5*f+ approach and flooded well under 4. Exception being poorly designed flooded that carry over at lower approaches.

The whole point of flooded is to get better approach. Check the suction & discharge sh. Compressor type?

 

[Cvhesteve]

The LL set point is currently 65%. I have not had a chance to check the LLS calibration. The EXV at full load is about 75% (going off the data logs I have available).

 

[patpinet]

Thank you sir, it’s a Smardt chiller (no oil) and less than 2 yrs old on new install so I would probably rule out dirt/oil issue. However I did notice the piping is undersized. It’s 2.5” supply/return and chiller design flow is 149GPM, I used B&G syzer to estimate velocity around 10fps. The friction loss is extreme around 15ft/100. Could you elaborate for me on how the higher flow velocity impacts approach?

With a simple google search I stumbled upon.
Max flow recommended at 2.5 inch is 75 gpm.
4 inch is the way to go.

At the evap what is the smardt pipe size, not the one from the building.

Just asking did you check flow? If so how much you got at the barrel?

Any log sheet available?

Envoyé de mon SM-G781W en utilisant Tapatalk

 

[moideen]

Smardt is not familiar to me; I didn't see him in Dubai. I've seen some new kinds of chillers that haven't been around for very long. They don't have enough money for internal R&D to make sure the quality is good. They will also buy all of the chiller's parts, like the EXV, compressor, control system, etc., which is why they can't show how reliable they are in operation.

 

[jwalkington]

Approach equals saturated versus leaving water temp differential. If you have too much water flow you can’t pick up the heat transfer. If you can slow down the water flow you may see a difference.

Hopefully installing contractor added gate valves just before / after end plate connections and you can check this one off pretty easily!