DB325: Lesson 3 - Principles of Heat Transfer and Conduction SAQ: Suggested Response - Q3

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This lesson allows you to test yourself on the material covered in the lesson on Principals of Heat Transfer and Conduction, and to determine the level to which you have met the learning outcomes.

Suggested Response - Q3

** Calculate the amount of heat that needs to be removed to cool 500 hL (52,650 kg) wort with SG of 1.053 from 90° to 20°C. The specific heat capacity of wort is roughly 4,000 J kg^-1 K^-1.

Response:

First, we need to decide if this is sensible or latent heat. Since there is a temperature change and no change in the wort's phase (it stays liquid), we know we are calculating the sensible heat. We can then recall the following formula:

$Q space equals space M C increment T$

To use this equation, we need the mass and heat capacity of the wort, and the initial and final temperatures. These values are all given in the problem statement.

We are now ready to enter our values into the equation and calculate.

$Q space equals space M C increment T$

$Q space equals space 52 comma 650 space cross times space 4 comma 000 space cross times space left parenthesis 20 space minus space 90 right parenthesis space equals space minus 14 comma 742 comma 000 comma 000 space J space equals space minus 14 comma 742 comma 000 space k J$

Note that the value calculated here is a negative number. This is because the heat has to be removed rather than supplied.

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Lesson 3 - Principles of Heat Transfer and Conduction SAQ

Suggested Response - Q3

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