The basic parameter is to determine the number of heat sources in order to accurately calculate the cooling load for a HVAC system. The heat sources can be the radiation heat energy from the sun, heat energy from the electrical or mechanical devices within the facility, heat from the light energy within the building or room, body heat from the persons sitting in the facility and conduction convection heat currents from the building structure. These all the heat sources must be accurately calculated in order to design an optimum HVAC unit. The facility contained the two bedrooms, one master bedroom, one kitchen, family living, guest living and foyer. The cooling load of all these sub-facilities is calculated accordingly. The next stage is to select the number of units and ton of refrigeration (T.R) based on the cooling load we calculated for the different sub-facilities.
The second last step in the HVAC designing is to design the duct. There are many methods for it but we chose equal friction method. There are many great reasons to select this duct design method. One of the reasons was that equal friction method did not really need the different velocities at different sections of the duct, making it simple and easy to implement. Finally the drawing will be made accordingly.
This report demonstrates the design calculations involved in a basic HVAC designing. It uses the certain calculations and assumptions based on the ASHRAE standards and relevant psychrometrics charts. The sole purpose for these calculations is to make sure to use accurate number of units based on the T.R so that the optimum cooling requirement fulfills at the minimum cost possible.
- To determine the heat load calculations by using different heat sources.
- To be able to understand and read the ASHRAE and certain psychrometrics charts & tables.
- To be proficient in assuming parameters accurately and in using certain relevant units involved in the refrigeration or HVAC.
- To be able to use number of units required based on the T.R results
- To be able to know how to use the cooling load calculation for different sub-facilities for a single system.
- To be able to design duct based on the chosen method.
- To learn to draw the diagram of the facility based on the designing.
The air conditioning part of the HVAC system involves not only the cooling of the air but it also helps in improving the overall quality of the air. This makes to feel comfortable for the occupants sitting in the facility. The certain calculations are being done based on the ASHRAE standards in order to find out the size and capacity of the units installed. The calculations also used the psychrometrics charts which is an important tool in determining different parameters related to heating or cooling load in a HVAC system. The report uses many values from these charts including the sensible and latent heat values. It also shows how the air will behave if the certain changes in humidity and temperature is brought. In short the psychrometrics charts help in determining certain air properties by not involving in tedious calculations.
The accurate results from the heat gain of building structure must be based on how accurately you used the coefficient values of the building walls and more importantly how accurately you used the temperature values.
The accuracy of the heat gain from sun is solely based on the accuracy of the Shade Coefficient. It must be wisely determined from the relevant tables.
The correct use of psychrometrics chart is important in determining the latent and sensible heat when it comes to calculate the heat from the occupants within the facility.
The calculations use the diversity factor to be 1 for the sake of simplicity. This can lead to minor discrepancy against the standard results for the calculation of heat load from the lighting inside the building.
It is wise to use the calculations divided for different rooms to get the more accurate results. The calculations used to combine the two rooms load into one in order to get the more optimum values of the capacity and size of the air condition unit. Moreover; the equal friction method was used to design the duct for the sake of simplicity. The other methods were also available but they tend to be more complex. The use of equal friction method can lead to some violations of the design but it can be tolerated for the simple HVAC design like this.
The report used the calculations and formulae based on the standard practice. It uses the table, charts, certain values and formulae based on the ASHRAE standards and certain psychrometrics charts & tables. For the more accurate results the whole facility is sub divided into different facilities and for each facility different capacity and size of the units are calculated. In the end the duct design based on the Equal Friction Method was calculated along with the facility design drawing.