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A water cooler of storage capacity 120 litres can cool water at a constant rate of P. In a closed circulation system (as shown schematically in this figure), the water from the cooler is used to cool an external device that constantly generates 3 kW of power (thermal load). The temperature of the water fed into the device cannot exceed 30∘C and the entire 120 litres of water is initially cooled to 10∘C. The entire system is thermally insulated. The minimum value of P for which the device can be operated for 3 hours (taking the specific heat capacity of water =4.2 kJ kg−1K−1 and the density of water =1000 kg m−3) is |
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Answer» A water cooler of storage capacity 120 litres can cool water at a constant rate of P. In a closed circulation system (as shown schematically in this figure), the water from the cooler is used to cool an external device that constantly generates 3 kW of power (thermal load). The temperature of the water fed into the device cannot exceed 30∘C and the entire 120 litres of water is initially cooled to 10∘C. The entire system is thermally insulated. The minimum value of P for which the device can be operated for 3 hours (taking the specific heat capacity of water =4.2 kJ kg−1K−1 and the density of water =1000 kg m−3) is |
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