Brief for Assignment 1 (Part A)

Introduction

1. The air-conditioning system or plant uses the most energy in a typical air-conditioned building in Singapore and may account for as high 60% of the overall electricity cost of a building. It is therefore imperative that in evaluating the energy performance of a building, there will be greater emphasis on the energy usage and performance of the building’s air-conditioning system.

The assignment focuses on evaluating the energy performance of the main chilled water plant of a centralized air-conditioning system. The chilled water plant to be evaluated is located at TP’s South Wing, which serves Blks 26A, 26B & 29A. Technical information of this chilled water plant and major components are provided in the student’s subject material package.

Objective of Assignment

2. To perform a Level II energy audit on the water-cooled chiller plant at TP’s South Wing by recording relevant performance parameters for various items of equipment.

Background on ACMV System in TP’s South Wing

3. The chiller plant serving TP’s South Wing will be the subject of our investigation. This system comprises the equipment listed in Table 1 on pg. 2, which are based on the 2 nos. of Carrier 23XRV VFD screw chiller as the duty and standby chillers.

4. The duty chiller will usually be 1 unit of the Carrier 23XRV VFD screw chiller. When the duty chiller operates, 1 x CHWP and 1 x CNWP will operate. On occasion, depending on the load, a 2nd chiller may operate. However, up to 3 x CTs may operate. Each CT is a triple-cell tower ie. there are 3 cells (each with its own fan) within each cooling tower.

5. There are another 2 units of Mitsubishi Heavy Industries (MHI) model ETI-50 which have been installed to serve future extensions. These are of 500 RT capacity each and supported by pumps and cooling towers identical to those for the Carrier chillers.

6. The plant’s operating schedule is 0715 hrs – 2115 hrs (Mon – Fri) and 0800 hrs – 1630 hrs (Sat). This amounts to a total operating duration of 4082 hrs/yr.

Parameters to be measured

4. The parameters to be measured for the overall air-conditioning system in TP’s South Wing are shown in Table 1 below:

Assignment Requirements

5. For this Assignment 1 (Part A), the main emphasis will be on gathering the data required for a Level II audit of the chilled water plant, and hence there will be no focus on the data for the airside of the air-conditioning system.

6. In addition, you are required to calculate the following:

a. The primary chilled water flowrate using the appropriate WPL formula and via the motor/pump speed. (Note: these are to be compared with the measured flowrate as provided by the EM flowmeter).

b. The bypass chilled water flowrate using the measured flowrates as provided by the appropriate EM flowmeters).

c. The condenser water flowrate using the appropriate WPL formula and via the motor/pump speed. (Note: these are to be compared with the measured flowrate as provided by the EM flowmeter).

Brief for Assignment 1 (Part B)

Objective of Assignment

The main objective of Assignment 1 (Part B) is to ascertain various performance parameters of the chiller plant, including the overall chilled water plant efficiency. In fulfilling the requirements, the following parameters shall be determined:

a. The cooling capacity of the chiller
b. The input power of the chiller
c. Efficiency (kW/RT) of the chiller
d. Part load (%) of the chiller
e. The input power of the various pumps (CHWP and CNWP)
f. The input power of the cooling tower fans (CTs)
g. Efficiency (kWRT) of the pumps
h. Efficiency (kW/RT) of the cooling towers
i. Overall kW/RT (Operating System Efficiency) of the chilled water plant
j. System heat balance (%) of the chilled water plant