Design Of The Cooling System And Indoor Air

Introduction

Residential dwellings are to be properly designed in order to serve the intended purpose; mainly providing conducive environment for the occupants.  Admittedly, a properly designed dwelling will offer a long-lasting impact on the dwellers and will even affect the behavior of the occupants in the long run. Notably, there are building services that must be incorporated into the building to meet the design requirements. The room air quality is therefore a fundamental aspect of the building services engineering. During summer, when room temperatures are likely to hit unimaginable highs, it is often imperative to provide artificial cooling to the room. Now, a cooling tower will be used for this purpose. This report presents a technical design work on the said building services engineering facility. Top on the list, is the fact that the room thermal performance must be in tandem with the environmental conditions of the area in which the building is to be seated. Majorly, the design work is split into three parts; the cooling tower pump design; Deriving and maintaining the indoor air quality and building psychometrics where aspects such as air temperature, humidity and general air quality are considered. In designing the cooling tower pump, the general dimensional characteristics of the building is needed. Notably, the information that has been provided to facilitate the design include: the suction pipe nominal diameter is 200mm with the cooling tower being on the 6^th floor. The elevation to 6^th floor from basement is 20m. The suction side has the globe valve, strainer, a horizontal pipe run 200mm in diameter; while the discharge side has got the gate valves, long radius 90^o elbow; 1 off globe valve, 1 off strainer, 20m long 200mm diameter pipe run. The cooling tower is to be installed in a residential single dwelling with 3 bedrooms, 1 dining, 1 kitchen, a home office and a toilet. Overly, the basic size of the house plan is 14 000mm x 15 000mm. On the other hand, the second and third portion of the project will be to determine the critical parameters that must be maintained in a room for proper indoor air quality. Psychometric analysis will come in handy in this section. Specifically, the following are determined: R and U values for the window, roof and floor which would then assist in determining the values of Q(sh); Q(lh) and outside airflow required per area. Here, the design standard AS 1668.2-2012 shall be used. Lastly, we shall use the psychometric chart to determine the outside airflow indoor condition point; mixing point Db and Wb hence outside air SH and LH will be calculated based on the provide room temperature. Importantly, therefore, the design work is aimed at deriving a workable system within the interiors of the room. Certainly, improvements to the system will be implemented only after several test trials are done.

Design Work

Part 1: Cooling tower pump

The following parameters are determined: Pump head, Q, NPSH, diameter, Power, pump selection, Head loss, water vapor pressure, Static head and atmospheric pressure:

Pump head= suction head +delivery head= 20m

Q=

Part2: Indoor Air Quality

Check the attached excel file

Part3: Psychometric chart

Based on provided catalogue (ducted split unit)

Select your indoor and outdoor unit and power requirement

Indoor power requirement=4.17kW

Rated power requirements= 12.5kW

Airflow rate= 900

Weight (indoor)= 65kg

Weight(outdoor)= 98kg  

• On psychrometric chart show the outside air point (1)

• On psychrometric chart show indoor condition point (2)
• On psychrometric chart show the mixing point (3)
• Calculate mixing point Db and WB
• Provide all values (DB, WB, RH, h, specific volume, moisture content of the points 1, 2, 3 including the units. 11. Based on provided room temperature calculate the required outside air SH and LH.