HVAC in air conditioning

heat transfer
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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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