Question

The performance test of an air conditioning unit rated as 140.7 kW (40 TR) seems to be indicating
poor cooling. The test on heat rejection to the atmosphere in its condenser shows the following:
Cooling water flow: 4L/s
$\text{Water temperatures: In}{30}^{\circ }C,out{40}^{\circ }C$.
A coupling is used to transmit power from the motor to the compressor with 95% efficiency
Power input to motor: 48 kW
What is the actual refrigeration capacity of the unit in TR?

• A. 44.1
• B. 39.2
• C. 36.4
• D. 34.7

Answer 1

The correct option is D 34.7

$\text{Heat rejected in condenser =}{m}_{\omega }{c}_{\omega }\Delta T$

$=4\times 4.1868(40-30)=167.5kW$

Work input

$W=48\times 0.95=45.6kW$

Refrigeration capacity by heat balance

$Q_{\text{ref}}=Q_{\text{Condenser}}-W$

$=167.5-45.6=121.9kW$

$=34.7TR$