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Objective of Cooling Load Calculation
What is the objective of Cooling Load Calculation ?
Calculating the cooling load is extremely important for any thermal engineer. There are multiple factors to take into account when calculating the cooling load. These factors are the air temperature and temperature in the HVAC and equipment.
The air temperature is the unit of measurement and is defined as the temperature with the air as a reference.
The temperature in the HVAC is defined as the temperature difference with the outside air.
Equipment must be sized for the environment in which it operates. A standard air conditioning system for a typical indoor environment is used.
This air conditioning system can be comprised of the following equipment
Cooling Air Conditioner
Boiler for heat transfer of heat in water from a source to the load.
If the ambient temperature is 25 °C and the wind speed is 2 m/s, the cooling load is:
The Cooling Load Calculation with Air Temperatures:
The cooling load can be calculated using the following formula:
2 l = V (t) + T (in)
To calculate the cooling load:
Find the outside air temperature to be 27 °C
Calculate the temperature of the air conditioning unit
Replace 20% of the outside air temperature with the temperature in the HVAC equipment
Replace the remaining 80% of the outside air temperature with the ambient temperature
Find the cooling load using this formula:
2 l = V (t) + T (in)
For example, with a 2:1 air-to-water conversion, the cooling load for a 2 kW air conditioning unit in a residential apartment would be:
2 kW = 25 °C + 27 °C = 37.7 °C
To calculate the cooling load, the air temperature must be 1 m above the air-conditioning unit. The ambient temperature in the apartment is at 2 m above the air conditioning unit.
Variations of cooling load calculation:
Vars
V al - Absolute temperature
f al - Relative air temperature
n al - Absolute water temperature
This formula can be divided in order to measure the air temperature of the other constituents of the air in the range of 0 to 37.7 °C
T al - Relative air temperature
P ater - Relative air pressure
A t - Absolute humidity
0 - Pressure
S ce - Relative humidity
V al = 1.125 * T al
V al = 1.875 * S ce
T al = 1.875 * A t
0.1 mS ce = 0.749 + 0.445 + 0.250 = 0.749 + 0.749 + 0.750 = 7.497
Maximum possible outdoor temperature + 7.497 × 87 = 115 °C
Mean outdoor air temperature + 7.497 × 87 = 106 °C
P ater = 1.8125 * V al
A t = 0.945 - T al
P ater = 1.125 * A t
Simplified formula for cooling load calculation:
2 l = V (t) + T (in) + T (al)
2 l = V al - T al + T al
2 l = V al - (T al - T al)
V al = 1.125 * T al
V al = 1.875 * S ce
To calculate the cooling load, the air temperature must be 1 m above the air conditioning unit. The ambient temperature in the apartment is at 1 m above the air conditioning unit.
Alcoolismus
Some other points to be aware of when calculating the cooling load:
Closed system: For an AC, the maximum temperature that the device is able to provide is between -30 to +10 °C (depending on outside temperature)
For an AC, the maximum temperature that the device is able to provide is between -30 to +10 °C (depending on outside temperature)
Room temperature: For an AC, the maximum temperature that the device is able to provide is between -20 to +10 °C (depending on outside temperature)
For an AC, the maximum temperature that the device is able to provide is between -20 to +10 °C (depending on outside temperature)
Vertical cross-section: For an AC, the maximum temperature that the device is able to provide is between 10 and 45 °C (depending on outside temperature)
For an AC, the maximum temperature that the device is able to provide is between 10 and 45 °C (depending on outside temperature)
Bases with non-overlapping directions: For an AC, the maximum temperature that the device is able to provide is between 0 to 10 °C (depending on outside temperature)
For an AC, the maximum temperature that the device is able to provide is between 0 to 10 °C (depending on outside temperature)
Specific air temperature: For an AC, the maximum temperature that the device is able to provide is between 0 and 10 °C (depending on outside temperature)
The ambient air temperature in the apartment (vertical cross-section) is measured 1 m above the air conditioning unit. The air conditioner's air temperature is the sum of all the air temperatures of the apartment. To calculate the cooling load, the air temperature must be above the air conditioning unit.
The purpose of Cooling Load Calculation is to determine the correct amount of cooling load to include in your application. Most industries (e.g., microcomputer applications) limit the loads and number of nodes used. This is also true for many applications of photovoltaic energy conversion systems.
It is possible to overload your application with unnecessary cooling.
If your application has to limit the number of cooling load nodes or overheating nodes in a cluster, make sure that you minimize the thermal stress in your cooling load calculation. If you are generating more heat than the cooling load can handle, you will get overheating. You will also get overheating if you have too many nodes.
Remember, you must stress the component under load to its limits, and the limits do not lie at zero degrees Kelvin.
Objective of Cooling Load Calculation in hvac is to make sure that you have the right amount of evaporative cooling for the amount of heating of your system. Based on the size of your system, you can add up to three cooling zones, each having its own evaporative cooling zone.
Zero-Emission Design
Increasingly stringent environmental regulations require manufacturers of HVAC equipment to reduce their carbon emissions and greenhouse gases. Modular HVAC systems are known to consume more power, up to 40-45% more than standard heating/cooling systems.
The introduction of electric heating and cooling units by some manufacturers has definitely contributed to the reduction of carbon emissions. Such systems can be connected to the mains and do not require the usage of gas or oil, thus making their installation energy efficient.
Reduction in Use of Gas or Oil
HVAC systems using oil and gas require periodic filling of the tank or with the use of a blower motor that recharges the oil. This can be very expensive for the owners of such systems. Electric HVAC systems offer a very long life, and it is an ideal choice for the owners of older properties, where the owners are not willing to spend on fuel.
Combustion of gas or oil also emits pollutants such as carbon monoxide, sulfur dioxide, nitrogen oxides, and lead which may impact the health of occupants. Electric heating and cooling units also emit fewer pollutants than the combustion of gas or oil. As a result, they tend to be popular with the building managers.
Convenience of Using the Same System in Different Parts of the House
Another benefit of the hvac system is that it can be operated on an efficient system with the help of the system controller. The controller can be purchased as a separate unit that is connected to the mains. With the help of the controller, you can select the zone and application for which the system should work. The system can be used for only one zone, or multiple zones.
Cleaning and Maintenance of the System
Though electric heating and cooling units are not supposed to produce any kind of residue, the floor fans installed in the system do generate heat. This can be easily removed using a floor cleaner. Though it is advised to clean and maintain the system regularly, most property owners do not follow this suggestion. The unnecessary use of gas, electricity, and water for maintaining the system increases the total cost of ownership of the system.
Final Thoughts
Electric HVAC systems provide a silent and safe way of heating and cooling the space that is not possible with the use of combustion equipment. In addition to saving you money, you can also control the temperatures of the system by way of a remote control.
The use of alternative sources of heating and cooling has really reduced the consumption of fuel and energy in most of the countries. With the help of these new technologies, you can be assured of the safe and comfortable space in your property.
Access Previous parts of this course, if you have missed them, by clicking Below...
How to Calculate External Static Pressure (ESP) with worked Example
How to Calculate Area of Sand Trap Louver with worked Example and detailed steps
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