Refrigeration and air conditioning

Principles of equipment cooling

You have studied the fundamentals and commercial refrigeration and air-conditioning systems. This final volume deals with another phase of your career ladder-equipment cooling. Since the principles of equipment cooling are common to all refrigeration systems, your mastery of the subject should be easy. All of the systems covered in this volume can be applied to commercial refrigeration and air conditioning.

To qualify you in equipment cooling, we will present the following systems in this volume:

• Direct expansion
• Absorption
• Centrifugal
• Water treatment
• Centrifugal water pumps
• Fundamentals of electronic controls
• Electronic control

JUST WHAT DO we mean when we say “direct expansion”? In the dictionary we find that the word “direct” means an unbroken connection or a straight bearing of one upon or toward another; “expansion” relates to the act or process of expanding or growing (in size or volume). Now we can see that a direct expansion system for equipment cooling is one in which the controlled variable comes in direct contact with the single refrigerant source, thereby causing the liquid refrigerant to boil and expand.

The centrifugal and absorption systems differ in that that they us a secondary refrigerantwater or brine-to cool the variable.