Thermodynamics

Calorimetry with flow rate

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A detailed solution is then proposed to you.

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A coil is immersed in a calorimeter.

Is passed through the coil a current of water.

is the specific heat of water.

At the input, the water is at a temperature of , the output is the calorimeter temperature which, through an electric heater, is maintained at .

Calorimetry with flow rate

Question

Calculate the power required from the heating resistance if the water flow rate through the coil is .

Indice

Consider using a similar assessment to that used for flowing gas in thermal machines.

Solution

Is selected as the closed fluid system in the calorimeter and a mass to the input at the instant .

At time , the system consists of the fluid in the calorimeter and a mass at the output, at the calorimeter temperature.

The first law of thermodynamics then gives : (assuming steady state)

Question

The resistance is ; calculate the current intensity .

Solution

Write :

So :

Question

Passing another liquid in the coil and for the same conditions (temperature and intensity), we must ensure a flow rate of .

Calculate the specific heat of the liquid.

Solution

We have the equality :

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