Lesson 9 - Refrigeration Technology SAQ
This lesson allows you to test yourself on the material covered in the Refrigeration Technology lesson and determine the level to which you have met the learning outcomes.
Suggested Response - Q6
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a) Discuss the following statement: It is essential to have a secondary refrigerant circuit when using ammonia as a primary refrigerant.
b) How would you reduce the amount of ammonia used?
Response:
a) Secondary refrigerants can be used to transfer the cooling between the primary refrigeration circuit and the users in the brewery. If the primary refrigerant is highly toxic, then using a secondary refrigerant circuit is the often the best course of action. Although ammonia is highly toxic, leaks are easily detected and contained using water sprays. If ammonia dissolves in water (or beer!), it forms ammonium. This means it can be used as both a primary and secondary refrigerant.
Ammonia is able to operate at a temperature range that is required in the brewery. Therefore, the temperature does not dictate a need for a secondary circuit.
Having a secondary circuit adds to capital cost, and energy losses are incurred because a second circuit has to be operated.
Thus, considering all of the above, having a secondary circuit for ammonia is not essential. So, the statement “It is essential to have a secondary refrigerant circuit when using ammonia as a primary refrigerant”, is false.
b) The amount of ammonia used can be reduced by using direct expansion plate heat exchangers, as opposed to shell and tube heat exchangers.
It may also be possible to place the heat exchangers in a central location and pump the beer and water to the heat exchangers (as opposed to pumping refrigerant to users in the brewery).