Chapter 1 introduction to refrigeration engineering

This module is about the Introduction to Refrigeration system

1. Engr Charlton S. Inao REFRIGERATION ENGINEERING

2. What is refrigeration Engineering? What is refrigeratioN ? The term  refrigeration  means cooling a space, substance or system to lower and/or maintain its temperature below the ambient one (while the removed heat is rejected at a higher temperature). In other words,  refrigeration  is artificial (human-made) cooling. What is refrigeration engineering? Refrigeration engineering refers to the  design, installation, repair and maintaining of   refrigeration  equipment in industrial and commercial buildings where food and other perishable goods are stored at a constant low temperature.

3. What Are the Different Types of Refrigeration Systems? Mechanical-Compression Refrigeration Systems. he most widely used refrigeration cycle method is mechanical compression. It has applications in both  air conditioning  and commercial and industrial refrigeration. As the name suggests, these types of systems transfer heat by mechanically compressing refrigerant into a low-pressure, cold liquid and expanding it into a high-pressure, hot gas. Refrigerants are substances that can boil at a wide range of temperatures with the application or removal of pressure

4. Cont ….. ike all liquids, they absorb heat when they boil into a gas and release it when they condense back into a liquid. The basics of the process deal with moving the refrigerant from the low-pressure side of the closed system to the high-pressure side. The liquid refrigerant boils at 40°F on the low-pressure side and absorbs heat from the warm indoor air. On the high-pressure side of the system, the heat travels from the 110°F vapor refrigerant to the cooler outdoor air, and the process repeats.

5. Absorption Refrigeration. Heat is also transferred in absorption refrigeration systems by compressing and expanding refrigerant. These systems rely on the process of absorption and heat, instead of an electrically powered mechanical compressor, to move the refrigerant from the low-pressure side to the high-pressure side. Unlike mechanical-compression refrigeration systems, which typically use  R-22  and  R-410A  for refrigerants, absorption refrigeration systems use refrigerants that other substances are attracted to and absorb.

6. Cont … For example, residential  HVAC chillers  often use ammonia as the refrigerant and water as the absorbent. The water is located in a component called the absorber, where it sucks ammonia from the low-pressure side of the system and removes heat while absorbing it. A pump sends the water-ammonia solution to a generator, which boils it, separating the ammonia from the water before sending it to the high-pressure side. In addition to the process of absorption, heat is also used to move the refrigerant throughout the system. The heat can derive from hot water, steam, natural gas or other fuel sources ]

7. Evaporative  Cooling . ... Unlike the mechanical-compression and absorption refrigeration systems discussed above, evaporative cooling doesn’t use the traditional refrigeration cycle. Instead, these units, often called swamp coolers, cool warmer outdoor air by blowing it over water-soaked pads as it enters the home. The water absorbs the heat from the air and evaporates. The cooler air is channeled into the home and the warm air out of it. Evaporative coolers can reduce air temperature by 15° to 40°F but are best suited for dry climates, such as those in the southwestern U.S. They’re also less costly to install and use about a quarter of the energy of central air conditioners.

8. Thermoelectric Refrigeration. Thermoelectric refrigeration systems are unique from the three other types of refrigeration in that no refrigerant or water is used. These systems use an electric current and a thermocouple. A thermocouple is made up of two different metal wires that are united at both ends. Insulation separates the rest of the wires from each other. When the current is directed on the thermocouple, one end will become hot and the other cool. Reversing the current’s direction has the effect of swapping the cold and hot junctions. The hot end will typically be placed outside of the area to be cooled with a heat sink attached to it to keep it the same temperature as the surrounding air. The cold side, which is below room temperature, is placed in the area to be cooled, attracting heat out of the air. This type of refrigeration is generally used for small cooling loads that can be difficult to access, such as electronic systems. Source : The Refrigeration School

9. What is the necessity of refrigeration food and meat preservation ? The fundamental reason for having a refrigerator is to keep food cold. Cold temperatures help food stay fresh longer. The basic idea behind  refrigeration  is to slow down the activity of bacteria (which all food contains) so that it takes longer for the bacteria to spoil the food.

10. What is a refrigeration cycle? The refrigeration cycle contains four major components: the compressor, condenser,  expansion  device, and evaporator. Refrigerant remains piped between these four components and is contained in the refrigerant loop. The refrigerant begins as a cool vapor and heads to the first component: the compressor. The compressor constricts the refrigerant vapor, raising its pressure, and pushes it into the coils on the outside of the  refrigerator . 2. When the hot gas in the coils meets the cooler air temperature of the kitchen, it becomes a liquid. ... The refrigerant absorbs the heat inside the  fridge , cooling down the air

11. Refrigeration Cycle TThe compressor constricts the refrigerant vapor, raising its pressure, and pushes it into the coils on the outside of the  refrigerator . 2. When the hot gas in the coils meets the cooler air temperature of the kitchen, it becomes a liquid. ... The refrigerant absorbs the heat inside the  fridge , cooling down the air T he compressor constricts the refrigerant vapor, raising its pressure, and pushes it into the coils on the outside of the  refrigerator . 2. When the hot gas in the coils meets the cooler air temperature of the kitchen, it becomes a liquid. ... The refrigerant absorbs the heat inside the  fridge , cooling down the air

12. Illustration

13. Coefficient of Performance The  coefficient of performance  or  COP  (sometimes  CP  or  CoP ) of a  heat pump, refrigerator or air conditioning system  is a ratio of useful heating or cooling provided to work required. [1] [2]  Higher COPs equate to lower operating costs. The COP usually exceeds 1, especially in heat pumps, because, instead of just converting work to heat (which, if 100% efficient, would be a COP of 1), it pumps additional heat from a heat source to where the heat is required. For complete systems, COP calculations should include energy consumption of all power consuming auxiliaries. COP is highly dependent on operating conditions, especially absolute temperature and relative temperature between sink and system, and is often graphed or averaged against expected conditions. [3]  Performance of  Absorption refrigerator  chillers is typically much lower, as they are not heat pumps relying on compression, but instead rely on chemical reactions driven by heat.

14. What is COP

15. Equation of COP