A water cooler of storage capacity 120 litres can cool water at a constant rate of P watts. In a closed circulation system (as shown schematically in the figure), the water from the cooler is used to cool an external device that generates constantly 3 kW of heat (thermal load). The temperature of water fed into the device cannot exceed 30°C and the entire stored 120 litres of water is initially cooled to 10°C. The entire system is thermally insulated. The minimum value of P (in watts) for which the device can be operated for 3 hours is : (Specific heat water is `4.2KJkg^(-1)K^(-1)` and the density of water 1000 kg `m^(-3))`

Options

A. `1600`
B. `2067`
C. `2533`
D. `3933`

Answer

B

Explanation

`3000-P = (120xx1)(4.2xx10^(3))(dT)/(dt)`
`(dT)/(dt) = (20)/(60 xx 60xx 3)`
`P = 2067W`