THERMODYNAMIC ANALYSIS OF AUTOMOTIVE HVAC SYSTEM.
Prof D.V.THAKUR 1,
1AISSMS’S POLYTECHNIC PUNE-01,
Department Of Mechanical Engineering, Pune - 01
A experimental set up has been developed for refrigeration circuits of automobile air conditioning systems. The experimental set up includes a variable capacity compressor and a thermostatic expansion valve in addition to the evaporator and micro channel parallel flow condenser. An experimental bench made up of original components from the air conditioning system of a compact passenger vehicle has been developed in order to check results from the model. The refrigeration circuit was equipped with a variable capacity compressor run by an electric motor controlled by a frequency converter. Effects on system performance of such operational parameters as compressor speed return air in the evaporator and condensing air temperatures have been experimentally evaluated and compared with theoretical by means of developed model. Theoretical results deviate from the experimentally obtained within a range. Effects of the refrigerant inventory have also been experimentally evaluated with results showing no effects on system performance over a wide range of refrigerant charges.
Keywords :Micro channel, Refrigerant, Parallel flow.
____________________________________________________________________ 2. INTRODUCTION
Not only do we depend on our cars to get us where we want to go, we also depend on them to get us there without discomfort. We expect the heater to keep us warm when it's cold outside, and the air conditioning system to keep us cool when it's hot. We get heat from the heater core, sort of a secondary radiator, which is part of the car’ cooling system. We get air conditioning from the car's elaborate air conditioning system. Despite its relatively small size, the cooling system has to deal with an enormous amount of heat to protect the engine from friction and the heat of combustion. The cooling system has to remove about 1400 KJ of heat per minute. This is a lot more heat than we need to heat a large home in cold weather. It's good to know that some of this heat can be put to the useful purpose of keeping us warm. Air conditioning makes driving much more comfortable in hot weather. Your car's air conditioner cleans and dehumidifies, the outside air entering your car. It also has the task of keeping the air at the temperature you select. These are all big jobs. How do our cars keep our "riding environment" the way we like it. Most people think the air conditioning system's job is to add "cold" air to the interior of the car. Actually, there is no such thing as "cold," just an absence of heat, or less heat than our bodies are comfortable with. The job of the air conditioning system is really to "remove" the heat that makes us uncomfortable, and returns the air to the car's interior in a "unheated" condition. Air conditioning, or cooling, is really a process of removing heat from an object. A compressor circulates a liquid refrigerant called Refrigerant−134a. The compressor moves the Refrigerant−134a from an evaporator, through a condenser and expansion valve, right back to the evaporator. The evaporator is right in front of a fan that pulls the hot, humid air out of the cars interior. The refrigerant makes the hot air's moisture condense into drops of water, removing the heat from the air. Once the water is removed, the "cool" air is sent back into the car's interior. 3. OBJECTIVE OF STUDY
To do thermodynamic study of automotive air-conditioning system and compare same with theoretical results. The system must be capable of keeping a temperature of 22˚C inside a stationary black vehicle with five occupants, with an outside temperature of 40˚C. Also, the system must be an efficient heating system, keeping an internal temperature of 15˚C with an outside temperature of...
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