Air Conditioning Design Assignment (solved)

What this assignment assesses.
This assignment is designed to assess the following:
 Your understanding of the characteristics and applications of the different types of air conditioning systems.

• Your ability to interpret design data.
• Your ability to use the psychrometric chart for the analysis of air conditioning systems.
• Your ability to analyse different types of air conditioning systems.
• ability to interpret and discuss system performance data.

Assignment
For the purpose of air conditioning, an office building has been divided into two zones, one on the east side and the other on the west side. Each zone is 30m x 6m x 3m high. The design data are as follow:

The following air conditioning systems are under consideration:

1. Four-pipe fan coil system with a ratio of secondary to primary air in each unit of 3:1 by volume.

The state of the air leaving the primary coil is 11.0 °C_db, 10 °C_wb. The temperature rise due to fan horsepower and duct gains in the summer is 2 °C. Assume that in winter the heat loss in the ductwork is equal to the heat gain due to fan horsepower. The primary air quantity, all fresh, supplied by the air handling plant is 2.5 l s^-1 m^-2 of floor area.
In winter the primary air is pre-heated in the air handling plant to 12 ^oC before it is distributed to the fan coil units.

2. A constant air volume terminal reheat system. The design fresh air (ventilation) quantity for both summer and winter is 2.5 l s^-1 m^-2 of floor area. In the summer the condition of the air leaving the cooling coil is 11 °C_db and 90 % relative humidity. The temperature rise due to fan horsepower and duct gains is 1.0 °C.

In winter the central plant delivers air to the terminal devices at 11 °C by mixing fresh air with recirculated air. It can be assumed that the heat loss in the ductwork is equal to the heat gain due to fan horsepower.
 Note: You can make suitable assumptions where necessary but these assumptions should be fully justified in your report.
You are required to:

1. For the Fan-coil system:

A 1.      Draw the schematic diagram of the system, stating the locations of the various air state points throughout the process. (5 Marks)
A 2.      Draw the psychrometric process of the plant, for both summer and winter design conditions (draw the process at the time of maximum load only), on the psychrometric chart provided. Indicate all the state points on the chart and specify the dry bulb temperature, the moisture content and the enthalpy at each point and include these values in a clear, tabulated form in your report. (20 Marks)
A 3.      Determine the refrigeration plant cooling capacity and boiler plant heating capacity based on your calculations. (10 Marks)

1. For the Constant Volume System

B 1.      Draw the schematic diagram of the system, stating the locations of the various air state points throughout the process. (5 Marks)
B 2.      Draw the psychrometric process of the plant, for both summer and winter design conditions (maximum load only), on the psychrometric chart provided. Indicate all the state points on the chart and specify the dry bulb temperature and moisture content at each point. (20 Marks)
B 3.      Determine the refrigeration plant cooling capacity and boiler plant heating capacity based on your calculations. (10 Marks)

1. Based on the values achieved in your answer, compare the two proposed systems in terms of:

C 1.     Running cost (5 Marks)
C 2.     Capital cost (Indicative figure, no numerical values are required) (5 Marks)
C 3.     Their ability to satisfy the design conditions. (5 Marks)
C 4.     Based on the outcome of C 1, C2 and C3, which System will you recommend? (5 Marks)
Method of assessment
Your answers will be marked on the clarity of your presentation, the accuracy of your calculations, the logic underlying your justifications and any assumptions you make, and the quality of your conclusions.