Water Cooled Machine IC81W

[magneticted]

Hi guys can anyone please give a estimation or rule of thumb for determining the heat loss fron a water cooled motor ( Heat Exchanger )For example we hae a 1Mw 4p motor with efficiency at FL of 95.8%, Water inlet is 33 Deg C , and oulet approx 39 Deg C, Water flow rate is 9.4 m3/h

 

[sreid]

At full load the energy loss based on the motor specs would be

1,000,000 x 0.042=42,000 Watt-sec = 42,000 Joule

Based on the water flow and temperature rise

100 cm^3 x 9.4 m^3/hr x 6 deg C / 3600 sec/hr = 15,666 cal

15,666 cal x 4.18 J/cal = 65,000 Joule

The difference between the two calculations could be caused by

Motor less efficient

Motor overloaded

Flow or temperature rise errors.

 

[aolalde]

kWloss = (liters/sec) x ( delta T) / 0.24 for water.

Since 9.4 cum/hr = 2.611 liters/sec, and delta T = 39-33 °C = 6 C

kWloss = 2.611 x 6 / 0.24 = 65.275 kilowatts.

 

[magneticted]

Thanks, however the kilowatt loss seems high. If this was a air to air cooled machine, then the heat loss as estimation we would say kw / effy = 43.84 kw (1043.84 - 1000 )

What we are trying to establish is the heat loss of this water cooled machine into the pump room. The water circuit will take a certain amount away, ( 65.275 kw ? )but some heat will still be transferred through the frame ( sides )maybe small but their will be 10 of these motors in this pump room

 

[waross]

It seems that the heat removed by the water cooling is more than the motor losses.
There are two possibilities;
1> The motor is running at a lower temperature than the room and is actually cooling the room.
2> The data is in error.
respectfully

 

[aolalde]

As WARoss stated, accuracy of temperature and water flow rate measurements is very important.

The water temperature rise is pretty straight to measure the energy it removes from the heat source.
It takes 1 calorie (4.184 joules) to increase 1 gram of water 1 °C.

 

[sreid]

It's difficult to say what the temperature will be in the pump room. However, the motor stator cases will be near the temperature of the cooling water. If the air temperature is higher than the motor case temperature, the heat will flow from the air to the motors. If you blow air around in the pump room with a fan to minimize air temperature stratification, the air temperature should not rise far above the motor case temperature.

There will also be cooling effects from the room walls and air leaks that are usually present.

 

[motorspert]

If the generator is at full load the losses are 44kW. My experience 90% of that will be taken by the water. leaving around 4-5kW loss into the room.

I was once told a rule of thumb that the heat loss was the centre height (in mm)/100. ie for a 710 machine it is approx 7.1kW. Its arbitrary and surprising how many times it comes close. Any want want to bet the centre height of this generator is 450mm?