Basic Composition Of HVAC System

- Jan 19, 2021-

(1) Basic composition of HVAC system


A complete and independent air conditioning system can basically be divided into three parts, namely: cold and heat sources and air handling equipment, cold and hot water delivery and distribution systems, and indoor terminal equipment.


In summer, the refrigeration equipment (cold source) provides cold water or liquid refrigerant, and in winter, the boiler (heat source) provides hot water or steam. The cold and hot water is sent to the air conditioning unit (air treatment equipment) through the cold and hot water distribution system. Process the air to the air supply point, and send the processed air into the room through the air distribution system to eliminate heat and humidity load, or send hot water to the end of the room (air treatment equipment) for heat exchange to meet the room load Requirement. Local treatment method A and centralized treatment method B can use the working principle of the HVAC system alone or in combination.

(2) Working principle


The main reason for the operation of the air conditioning system is the principle of refrigeration, namely the reverse Carnot cycle.

The Carnot cycle consists of four cyclic processes, two adiabatic processes and two isothermal processes. Carnot and Son of NLS 1824 conducted a theoretical study on the maximum possible efficiency of heat engines. Carnot assumes that the working substance is only related to Two constant temperature heat sources exchange heat without loss of heat dissipation, air leakage, friction, etc. In order to make the process a quasi-static process, the heat absorption of the working substance from the high temperature heat source should adopt an isothermal expansion process with no temperature difference. Similarly, release The heat to the low temperature heat source should be an isothermal compression process. Due to this limitation, it can only exchange heat with two heat sources, and can only be an adiabatic process after being separated from the heat source.