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 - Q1
* Explain the difference between the following:
a) Primary and secondary refrigerants
b) Ozone depletion potential and global warming potential
c) Natural and synthetic refrigerants
d) Flooded and direct expansion evaporators
Response:
a) Primary refrigerants are used for the generation of refrigeration (primary refrigeration), normally through mechanical means. They are primarily chosen for their ability to be condensed and evaporated effectively under the conditions required by the refrigeration equipment. Secondary refrigerants are used to transfer the refrigeration from the primary refrigeration to the point of use in the brewery. They are chosen for their ability to effectively transfer heat.
b) Ozone depletion potential (ODP) gives an indication of a refrigerant’s impact on the ozone layer. The values range from 0 (where the substance has no impact on the ozone layer) to 1 (where the substance has the most harmful impact on the ozone layer).
Global warming potential (GWP) indicates how much the refrigerant contributes to global warming. It is measured in relation to CO2, which is deemed to have a GWP of 1. The values range from 0 to several thousand.
c) Natural refrigerants are refrigerants that occur in nature. Some of these are processed from natural sources, whilst others such as ammonia are manufactured. Synthetic refrigerants are man-made and do not occur naturally.
d) With flooded evaporators, the liquid refrigerant covers the entire heat transfer surface. Direct expansion evaporators are designed to fully vaporise the refrigerant. At full design capacity, approximately 20% of the heat exchanger will contain vapour.