HVAC in air conditioning

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Introduction
Air-Conditioning is a process of treating air for the comfort requirements of the
occupants in the conditioned space. The properties of air can be modified, by undergoing
certain thermodynamics processes. The most basic of processes involved in air-conditioning
is heating, steam humidification, simple cooling, and dehumidification.
Objective
To observe and understand the changes in air properties as it is treated in a basic air-
conditioning unit.
Theory
Heating, Ventilating, and Air Conditioning, or HVAC for short, is one of the sub
disciplines in Mechanical Engineering. It involves thermodynamics, fluid mechanics, and
refrigeration.
HVAC was studied with the purpose of either heating, or cooling a building to
achieve a sensible heat range, and thermal comfort.
HVAC can be performed using several known method such as using refrigerants and
cooling tower, blowing air through an ice block, and district cooling.
Usually, a building uses refrigerants, air handling unit or AHU, and a cooling tower as
its component in air conditioning. The chilled water is pumped throughout the building and
enters the AHU, which will then blow the outside air through a radiator flowing with the
chilled water. As a result, the flowing air become cooled, and then blown to the required
space. This method is used to support only one building because it uses a smaller amount of
refrigerants compared to district cooling.
Another method used is district cooling. The concept is the same as a cooling tower,
but instead of a cooling tower for each building, district cooling uses one whole building as
its cooling tower to supply chilled water to a specified district. The building will pump water
from a nearby source, cools it down, and then pumps it to the surrounding building using
underground pipes. When the chilled water reaches the target building, it will flow through a
heat exchanger or HEX. The target building will have their water source that will absorb the
coolness from the HEX and then pumped into the AHU.
Next are the ice blocks. The building will start the ice making process during the night
time, when there are no tenants around, and when the electricity tariff is lower. The ice
making room is very huge, so that it can store as much ice blocks required. And when the
process is complete, during the day, they will just blow the air through the ice blocks, thus
dropping the air temperature, and cools the air.
As for the heating in HVAC, sometime they just provide hot water to the target
building, and sometimes, the return of chilled water from the building that uses chilled water
for its air conditioning, is used back in another building to supply heat. And if the water is not
warm enough, they will just have to heat up the water to boost its temperature.


Procedure
1. This experiment had been divided into four stages which there were;

I. Stages 1 -No Process, where in these stages it was act as the
control data. All the data and psychometric chart before the
experiment had been print out and used as the reference and
comparison data.
II. Stages 2-Sensible Heating.
III. Stages 3-Steam Humidification.
IV. Stages 4-Cooling and Dehumidification.

2. In stages 1, as the Computer Linked Air Conditioning Laboratory Unit was activated the initial
data were taken by printing the data and psychometric chart from the computer. Then, the data
were written in the result of data table and print out (schematic diagram no.7 and psychometric
chart no.8). The difference between the temperatures in and out was calculated and recorded.

3. In stages 2, here there were two kind of data needed, first the one that get
from activated of pre-heated at 1kW and second from both of activation
of pre-heater which at 0.5kW and the re-heater. For the first data as the air
flow inside, the pre-heater was activated by clicking the first switch on.
Then it was let to activate for next 5 minutes. After that the data was print
out (schematic diagram no.32 and psychometric chart no.33). The
difference between the temperatures in and out was calculated and
recorded.

4. When it finished, preheater was activated with preheated
leave activated, hence the total power need to preheat and re-
heated were 1.5kW and then leave for another 5 minutes. Then the data
were printed (schematic diagram no.46 and psychometric chart
no.47).The difference between the temperature in and out were calculate
and recorded.


5. In stage 3, the entire water heater was activated in order to
accelerate the time taken to boil the water inside the boiler to
producing the steam. The speed of the fan had been reduced to 25
rpm in order to help to detect the steam within vicinity.




6. After the steam were detected, two switch of 2kW of heater were
deactivated and only one 3kW heater was leave activated. Then the
speed of fan rise to 35 rpm and leave for 5 minutes before the data
were taken. As the 5 minutes passed, the data were printed out
(schematic diagram no.56 and psychometric chart no.57). The
amount of steam, the change of humidity and corresponding rise of
temperature had been calculated and recorded in the table.

7. In stage 4, the compressor of the refrigeration was activated allowed
the temperature to cool down at the range of 18°C-20°C and
stabilized. After 5 minutes the data was taken and print out
(schematic diagram no.67and psychometric chart no.68). As the
temperature started to stabilized, the time taken for the system
collecting the 100ml of water were taken from the first drop until
the last drop of 100ml. Then, the rate of condensation process was
calculated and recorded in the table.


















Apparatus
Computer Linked Air Conditioning Laboratory Unit (P.A Hilton)



Computer
Printer

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