Air Conditioning Laboratory Project 99. 10
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1. Measure the diameter of the coil. Count the number of coils that are first hit by the air and the total number of coils for each exchanger (for every U shape seen, there are two coils running through). Find the coil surface temperature. Find velocity of the air entering the coils. Find the temperature of the air entering the flow over the coils. With the humidity sensor, take relative humidity and temperature readings of the air near the cool side of the air conditioner. Repeat step 6 at the other locations on the air conditioner. Analysis: Using the tables in the back of the Heat Transfer book find the relevant properties of the air using table A4. Air properties using temperatures of the inlet and the coil surface. Using the given equations, find the convection heat transfer rate. Looking at the temperature and the relative humidity data, is this a comfortable atmosphere? The Ideal Air-Conditioning Cycle Objectives: To determine the coefficient of performance (COP) of a window air-conditioner using the assumptions of an ideal vapor-compression refrigeration cycle. To determine the rate of heat removal from the refrigerated space and heat rejected from the refrigerant to the environment. To determine the power into the compressor. Background: The ideal vapor-compression refrigeration cycle is the most commonly used/assumed cycle for air-conditioning. This cycle in made-up of four processes: Isentropic compression in a compressor. Heat rejection in a condenser coil, P = constant. Expansion in the throttling valve. Heat absorption in an evaporator coil, P = constant. 
(Figure 1) For an ideal cycle the refrigerant enters the compressor as a saturated vapor and is compressed isentropically. The temperature increases during the compression. The refrigerant enters the condenser as a superheated vapor and leaves as a saturated liquid. The pressure and temperature both drop as it passes through the throttling valve. The refrigerant then enters the evaporator as a low quality mixture and evaporates completely as it absorbs heat from the surroundings. All four parts can be modeled as steady-flow devices. The change in kinetic and potential energy are usually small compared to the work and potential energy terms. The conservation of energy equation reduces to: q – w = he - hi (eq. 1) T  he condenser and evaporator do not involve any work. The compressor can be approximated as adiabatic. The COP of an air conditioner can be expressed as:  (eq. 2) (eq. 3)
In the ideal case h1 = hg@P1 and h3 = hf@P3. Relevant Equations: Download 1.59 Mb. Share with your friends:
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