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sihombing
08-07-2006, 11:32 AM
Dear All,
i was doing testing and commisioning of AHU unit yesterday when i found that the water cooling condenser create unusual noise and vibration.

This had never happened to me before. can you guys give me an advices regarding this?

I don't know where the noise comes from but i suspect the pipe inside the condensor is too small and the water velocity flows thru the pipe is quite high.
I took the measurement and found that water velocity flowing through condenser is 8 m/s. Is this acceptable?

thanks for your suggestions...

NoNickName
09-07-2006, 08:59 AM
No, it is not. Can you check the water flow against published data of that condenser?

sihombing
10-07-2006, 03:14 PM
thank you Nonickname...This is the details :
AHU cooling capacity : 146 kW
Compressor power : 142 kW
Condenser cooling capacity : 200 RT (200x12000 BTUh)
Condenser cooling water flow : 35 m3/hr
Entering water temp : 32 deg.C
Leav. Water temp : 41 deg.C

I think the size of condenser is too big. Isn't it?

NoNickName
11-07-2006, 10:30 AM
Uh?
200RT are 703kW. On 5°K in to out it would result in a 33.5 l/s or 120.6 m3/h.
It matches the compressor capacity of 142kW and a COP of approx 4 (142x4 + 142 = 710), but not the AHU cooling capacity which should be 142x4 = 560/570 kW. The condenser water flow is highly insufficient and would explain the high delta of 9°K (41-32).
A messy installation, I reckon...

NoNickName
11-07-2006, 10:34 AM
And BTW, normal water bundle crossflow velocity in a water condenser should be in the range of 0.8-1.5 m/s

S.K.VARDE
12-07-2006, 11:50 AM
Figure given by you does't matches.

200 TR (703 KW) condenser is about 4 times bigger.

you may go for replacement of condenser of matching capacity.

as suggested by noNickName the water velocity should be in the range of 0.8 to 1.5 m/s.

You did't specify the refrigerant. If it is a Ammonia, bigger size may not be a problem. even it is too big.

US Iceman
12-07-2006, 02:28 PM
The high water velocity could be inducing tube vibration also. If the tubes are not supported well in the condenser shell, they can vibrate between the fixed ends in the tube sheet.

However, I wonder how the tube side water velocity could be too high if the TD for the water is 9 degrees.:confused:

sihombing
12-07-2006, 03:32 PM
The refrigerant used is R 404A. i fully agree with you that the condenser size is too big...

The initial story :
my bos wants to source new supplier for the condenser. this condenser is cheaper S$ 1500 :D hehehe. i don't know whether they had tested or not before.
i only do the testing and commisioning for this anchor handling/tug supply vessel and do not involve since the beginning.

the final story : the vessel will be sailing to Abu Dhabi tmrw. Owner rejected the condenser because of the noise. He said to my boss " See you in Abu Dhabi" :p. It means we must buy two condensers for replacement, send it to Abu Dhabi, send technicians there,.....blablabla..Gosh, it will cost more than S$ 16.000.

i finally realize, delta Temperature 9 deg. C for condenser (T in 32 deg C and T out 41 deg C) cannot be achieved in Abu Dhabi...what a poor design.

sihombing
12-07-2006, 03:37 PM
The compressor located in different (side by side)compartment. Condenser room is well insulated by using A-60 insulation. So, we can ignore compressor noise for this case.