Basic Refrigeration System
Refrigeration system is a combination of mechanical and electrical devices designed for heat absorption and extraction purposes. It is made of tubing connected in series where refrigerant circulates and undergoes evaporation and condensation process repeatedly. Refrigeration system is almost similar with the human circulatory system in which blood circulates through blood vessels to convey oxygen and nutrients to vital parts of the body.The human heart is the center of the circulatory system where blood is being drawn and pumped repeatedly as the cycle continuously taking place.
Basic Parts of Refrigeration System
Compressor is a mechanical device driven by electrical or external mechanical energy that causes the refrigerant to circulate to the system as it absorbs and dissipate heat. It is considered as the heart of the system.
It draws vapor refrigerant with low pressure and temperature containing heat and compresses it into high temperature and high pressure vapor, to create and maintain temperature difference between the super heated vapor and the outside temperature of the condenser coil in order for the heat that has been carried by the vapor refrigerant to transfer to another body ( air or water).
Condenser is part of the system where refrigerant having vapor form (containing heat ) starts giving off the heat that has been absorbed from the evaporator changing its phase into liquid with high temperature and pressure.
Remember ,when heat leaves vapor substance, condensation takes place and such vapor will turn into liquid, this process happens in the condenser as heat is being released due to the temperature difference between vapor refrigerant and the outside air due to the compression action of the compressor that increases its pressure and temperature.
Refrigerant Metering Device
This is also called as refrigerant flow control device. Its purpose is just to control the flow of liquid refrigerant from the condenser going to the evaporator. Controlling the flow of refrigerant satisfies the need of the evaporator to have only enough amount of liquid refrigerant based on the amount of heat that is going to be absorbed.
The flow of liquid refrigerant given by the metering device depends on the heat load. As the heat surrounding the evaporator coil increases,metering device will supply more liquid refrigerant that is enough only to absorb such heat and evaporate, ensuring that there will be no liquid refrigerant entering the compressor since liquid is in-compressible fluid. Metering device also creates low pressure of the system giving the refrigerant enough space to expand as it absorbs heat in the evaporator.
Evaporator is part of the system in which refrigeration process starts. It is the place where refrigerant absorbs heat to be given off at the condenser. Liquid refrigerant at minimal amount enters the evaporator coil as supplied by the metering device, this creates a sudden low pressure to the liquid refrigerant.
Evaporator is the one that is subjected to be put in a certain confined space to be cooled or to where heat must be removed. As the outside surface of the evaporator coil directly exposed to the air in a closed space, the heat from that space will be sensed by the liquid refrigerant inside the evaporator coil.
This causes the heat to travel via conduction from the outside air to the outside surface of the tube or coil going to the inside surface of the tube to the liquid refrigerant. As the refrigerant absorbs heat, it evaporates and change its phase into vapor ( chemical change due to the presence of heat) The process is called evaporation.As the heat continuously transferring to the refrigerant inside the evaporator coil, temperature is getting lower inside the confined space where evaporator coil is placed. The absence of heat means cold.Vapor refrigerant with low pressure and temperature will now leave the evaporator coil carrying heat as it takes into vapor form and enter into compressor. Compressor will again do its role.
High Side and Low Side of the System
Low side is point of the system where refrigerant undergoes low temperature and pressure. At this point the direction of heat is from the outside air or from the surrounding going to the refrigerant within the system. The refrigerant changes its phase from liquid to vapor. This point starts from the exit point of metering device up to the inlet of the compressor. It is noticeable when looking into the actual system that the size of tubes used in this part of the system is larger than the high side of the system. This explains that the greater the volume or space fluid occupies, the lower the pressure.
This is the point where refrigerant undergoes high temperature and pressure and the change of state is from vapor to liquid. The direction of heat flow is from the refrigerant going to the outside surface of the air. High side point starts at the discharge line of the compressor up to the inlet of the metering device. This uses smaller tube diameter compared to the low side of the system.