Lab Sheet Air Cond

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1.0 Introduction
Air-conditioning is a widespread feature of building engineering, designed to make the
occupants feel comfortable and at ease. The main functions of an air-conditioning system
include heating and cooling, and humidifying and dehumidifying in order to create the
desired indoor air conditions.
The Air-Conditioning Unit includes all the components found in air-conditioners installed in
buildings. It additionally has a complete refrigeration unit, enabling the system to cover most
of the spectrum of experiments in the field of refrigeration and air-conditioning engineering.
In compiling the exercises, care was taken to achieve a didactically logical sequence. The
first element is a theoretical introduction to the individual components and their mode of
functioning. Later the principles are investigated in more detail on the basis of experiments.
This does not only involve calculations; rather, the greater part of the evaluation procedure is
carried out with the aid of graphs. The measured values are display on digital indicators for
recording and calculation purposes.

2.0 Unit Design
2.1 Unit Construction
Figure 1 shows schematic diagram of the air conditioning system.

Figure 1: Unit Construction for Air Conditioning Unit (Model: AC 01)

1. Control Panel

9. Refrigerant Flow Transmitter

2. Expansion Valve

10. Humidity/Temperature Sensor

3. Orifice

11. Fan

4. DP Transmitter

12. Humidifier

5. Heater

13. Sight Glass

6. Pressure Switch

14. Refrigerant Pressure Transmitter

7. Refrigerant Condenser

15. Filter Dryer

8. Refrigerant Compressor

The air-conditioning unit principally consists of two assemblies:
a. Air-conditioning system
b. Refrigeration unit

2.2 Air Conditioning System
Based on the various measurement locations, the schematic for the complete air-conditioning
system is as follows.

Figure 2: Process Schematic Diagram for Air Conditioning Unit

The air-conditioning system comprises the following components:


Combined Temperature / Relative Humidity Transmitter

A measuring probe consists of a temperature sensor and a relative humidity sensor.


Radial Fan

The air volume flow can be varied with the aid of a speed adjuster.


Steam Humidifier

The steam air humidifier has an electric power consumption of 2 kW.


Pre-heater

The pre-heater consists of four electric air heaters, each with an output of 0.5 kW. The
individual heaters are configured to enable heating powers of 0, 1 and 2 kW to be set.


Evaporator

The evaporator used is the direct evaporator of a refrigeration unit.


Re-Heater

The re-heater is constructed in exactly the same way as the pre-heater. The individual air
heaters only deliver an output of 0.25 kW, however, which means a maximum heating
power of 1 kW is achieved.


Orifice

Mass flow rate can be calculated from the orifice correlation by measuring differential
pressure across the orifice.

2.3 Refrigeration unit
The refrigeration unit circulates the refrigerant R134a. The following schematic shows the
circuit, and the components of the unit.

Figure 3: Process Schematic Diagram for Refrigeration Unit

The labelled components are:
i)
ii)
iii)
iv)

Compressor
Condenser
Expansion valve
Evaporator

The temperatures and pressures in the refrigerant circuit are recorded by electronic sensors
and indicated on digital indicators. The volume flow of the refrigerant is measured with the
aid of a flow transmitter.
There are 4 basic processes or changes in state of the refrigerant occur in a VapourCompression Refrigeration Cycle. These 4 processes shall be illustrated in the most simplistic
way with the aid of above Schematic Sketch.



Compression Process (1 to 2)

Refrigerant at point 1 is low temperature and low Pressure gas. In order to be able to use
it again to achieve the refrigerating effect continuously, it must be brought back to liquid
form at a high pressure. The first steep in this process is to increase the pressure of the
refrigerant gas by using a compressor. Compressing the gas also results in increasing its
temperature.


Condensing Process (2 to 3)

The refrigerant leaves the compressor as a gas at high temperature and high pressure. In
order to change it to a liquid, heat must be removed from it. This is accomplished in a
heat exchanger called the condenser. The refrigerant flows through air finned condenser
and cooled down by surrounding air facilitate with electrical fan. Heat is therefore
removed from the refrigerant; the refrigerant condenses to a liquid state at point 3.


Expansion Process (3 to 4)

Refrigerant at point 3 in liquid state with a relatively high pressure and temperature will
flow through a restriction called the flow device or expansion valve. The refrigerant loses
pressure going through the restriction therefore a small portion of the refrigerant flashes
(vaporizes) into a gas. In order to vaporize, it must gain heat (which it takes from that
portion of the refrigerant that did not vaporize), thus resulting in cooling by a low
temperature.


Vaporizing Process (4 to 1)

The refrigerant flows through a heat exchanger called the evaporator. The fluid to be
cooled is at a slightly higher temperature than the refrigerant, therefore heat is transferred
from it to the refrigerant producing the cooling effect desired. The refrigerant boils
because of the heat it receives in the evaporator. By the time it leaves the evaporator at
point 1 it is completely vaporized.
The refrigerant has thus returned to its initial state and is now ready to repeat the cycle, in
a continuous manner.

2.0 Theory
Students need to develop by themselves the fundamental of air conditioning system according
to thermodynamics principles. This part should cover cyclic process of the air conditioning
system and it processes on T-s and p-h diagrams. Students also need to explain equation
involve in order to determine performance of the system. Your theory should reflect to
objectives.

3.0 Objective
1)
To determine the effect of radial fan speed, preheating process and reheating
process on the relative humidity, air temperature in air conditioning system
regards to human comfort.

4.0 EXPERIMENTAL PROCEDURE

4.1 General Start-up Procedure
1. Perform a quick inspection to ensure that the unit is in proper operating condition.
2. Make sure the humidifier water supply is connected to a tap water source.
3. Connect a drain hose to the condensate collector at the bottom of the air duct.
4. Turn on the power supply switch.
5. Switch on the main power switch for the air

4.2 Procedures
1. Adjust the preheater power to 1KW and the re-heater power to 0.5KW
2. Set the radial fan speed to 0 for the first data collection.

3. Allow the refrigerant system as well as the preheater and re-heater coil to reach steady state
which require approximately 15 minutes
4. Start the stopwatch after the red light indicator of the preheater and re-heater respectively
switch off
5. Record the reading after 3 minutes for our objectives respectively in which the first
objective require the value of AH1,AH2,AH3,AH4,AH5,AT1,AT2,AT3,AT4 and AT5.
6. Record the value of PT1, PT2, TT1, TT2, TT3, TT4 and TT5. Repeat the step 6 and step 7
by manipulating the air speed ranging from 0, 35%, 70% and 100%.
7. Tabulate the result.

4.3 General Shut-down Procedure
1. Switch off the pre-heaters and re-heaters and allow the heaters to cool down with fan on.
2. Turn off the fan speed control knob, then the fan switch.
3. Make sure that all other switches on the control panel are switched off.
4. Switch off the main switch and power supply.
5. Close the tap water supply.

5.0 Results
Record required data for analysis.

6.0 Discussions
Discuss outcomes of the result based on the experimental data obtained. You may apply your
understanding in thermodynamics principles. Show all graph, chart, calculation process
involve. You may use the attachment given.

7.0 Question
a. State 3 differences of an Air Conditioning unit and a Refrigeration unit.
b. There is a chart that usually referred when dealing with the parameters regarding
surrounding air and cooled air (not refrigerant) especially if using an Air Conditioning. Name
that chart and state five (5) parameters that can be obtained from the chart.
c. Define and explain the functions of four essential equipments in an Air Conditioning.

8.0 Conclusion
Based on the experiment, draw your own conclusion.

9.0 References
State any references used. Make sure your report should not use website link as you
reference. A

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