INTRODUCTION 3

CHAPTER II 4

CHAPTER III 6

AIR-CONDITIONING SYSTEM AND COMPONENT MODELING 6

3.2.4 Expansion Valve 12

3.2.5 Evaporator 13

4.1 Objectives 18

4.2 Methodology 18

CHAPTER V 21

Analysis of the Existing System (A*TR) 21

OPTIMIZATION OF OPERATING PARAMETERS 25

6.1 Optimization 25

7.1 CONDENSER 29

7.1.1 Varying the Number of Rows and circuits of Condenser coil 29

7.3 CONDENSER FAN 37

7.4 COMPRESSOR 37

8.1 Objective 39

8.2 Procedure and Planning 39

8.7 Experimentation 43

8.8 Difficulties & Solutions: 44

APPENDIX A 48

APPENDIX B 50

CHAPTER I

INTRODUCTION

CHAPTER II

Carrier Aircon

2.1 Carrier Aircon

Carrier Aircon is the global leader in the field of air-conditioning and refrigeration. It is an important member of United Technology Corporation, UTC, an umbrella organization of seven companies. Carrier is one the most widely present group, precisely in more than 20 countries. Its European and US counterpart give Carrier India access to latest technologies and a wide product base in the industry. The capacity utilizations levels have been consistently high.

Carrier Aircon has always maintained its commitment to the quality of its product. In recent times, Carrier India has undergone some fine tuning to be geared for the next round of competition. It has got a new MD Mr. Zubin Irani with previous MD being given higher responsibilities in the global headquarters of UTC in US. As per Mr. Zubin, Carrier will carry on its stress on quality and will expand its Engineering section, which is primarily taking care of R & D.

2.2 About Gurgaon Plant

4. Other required buildings are also present. We have a hospital and a well furnished workers’ canteen.

2.3 Ranges of Products

Carrier Aircon manufactures almost complete range of products in the field of air-conditioning. It various products are listed below

Table 2.1 CARRIER’S Products Range

CHAPTER III

AIR-CONDITIONING SYSTEM AND COMPONENT MODELING

3.1 Refrigeration Cycle

Heating, Ventilating, and Air-Conditioning (HVAC) systems that provide a cooling effect depend on a refrigeration cycle. Both the control and performance of HVAC systems are significantly affected by the performance of the refrigeration cycle. Therefore a basic understanding of the refrigeration cycle is needed in the design and optimization of HVAC systems. Of the three basic refrigeration cycles (vapor compression, absorption, and thermo-electric), the cycle typically used in the HVAC industry is the vapor compression cycle. Vapor compression refrigeration has many

3.2 System Component Models

3.2.1 Compressor:

3.2.2 Condenser:

The condenser is a heat exchanger that rejects heat from the refrigerant to the outside air. Although there are many configurations of heat exchangers, finned-tube heat exchangers are the type most commonly used for residential air conditioning applications.

Figure 3-2: Typical Cross Flow Heat Exchanger (fins not displayed)

where m is the mass flow rate of fluid and cp is the specific heat of the fluid. The heat capacity, C, is the extensive equivalent to the specific heat, and it determines the amount of heat a substance absorbs or rejects when the temperature changes.

The amount of air flowing over each section of the condenser is proportional to the tube length, L, corresponding to each specific section. For example, the mass of air flowing over the saturated section of the condenser can be found by the following relation

Furthermore, the plates of the heat exchanger prevent mixing of the air flowing over the fins. Therefore, air at one end of the heat exchanger will not necessarily be the same temperature as the air at the other end. For a cross flow heat exchanger with both fluids unmixed, the effectiveness can be related to the number of transfer units (NTU) with the following expression (Incropera & DeWitt, 1996):

The NTU is a function of the overall heat transfer coefficient, U, and is defined as

3.2.3 Condenser Fan:

Natural convection is not sufficient to attain the heat transfer rate required on the airside of the condenser used in a reasonably sized residential air-conditioning system. Therefore a fan must be employed to maintain the airflow at a sufficient rate of speed. Although much of the power consumed by the total system is due to the compressor, the condenser fan also requires a significant amount of power. The power required by the fan is directly related to the air-side pressure drop across the condenser and to the velocity of air across the condenser:

3.2.5 Evaporator:

The ratio of the sensible heat enthalpy change to the temperature change is by definition, the specific heat, cp. Therefore, after substituting cp into (3-24) and rearranging, the following expression is obtained:

After the air flows over the evaporator, it enters a series of ducts that then return the air back inside the living space. The power required by the evaporator fan depends on the losses in these ducts and can vary from configuration to configuration. Therefore, the default power requirement used by the Air-conditioning and Refrigeration Institute (ARI, 1989) of 365 Watts per 1000 ft3/minute of air will be used.

3.2.7 Refrigerant Mass Inventory:

The boundary conditions for the saturated portion of the evaporator are

where l is integral variable evaporating tube length and L is the total evaporating tube length. Using the boundary conditions and assuming the quality varies linearly with tube length, the following expression results

Integrating (3-34) yields the following expression

And

CHAPTER IV

PROJECT DETAILS

4.1 Objectives

2) The geometric design parameters

for the air-cooled condenser coil of a vapor compression residential air-conditioning system of capacity A* TR and B* TR with R-22 as the working fluid. The condenser and total system operating conditions are varied so that the system’s capacity can be evaluated as a function of the heat exchanger design.

But with this growing industry now there is very less margin left to the AC’s manufacturing companies. So the strategy of gaining maximum profit by minimizing the manufacturing cost is striving. For this companies have developed their Research and development departments that work for the continuing update the product and have the major responsibility of holding the market share.

4.2 Methodology

As the most important issue in any project is the clarity on objectives, we started with clearly defining what we sought and how we proposed to implement it. The process followed by us can be summarized as

4.3 System Design

4.4 Optimization Parameters

2) Geometric design parameters specific to the condenser coil.

As part of the optimization process, comparisons are made between condensers of various geometric configurations (tube diameters, fin spacing, etc.). However, it is not possible to make valid comparisons between different heat exchanger configurations without first optimizing the operating parameters at each configuration to yield the maximum capacity. For example, it is erroneous to compare the performance of a system with a 3-row condenser coil configuration in which the operating parameters have been optimized to system with a 2-row condenser coil configuration in which the operating parameters have not been optimized. No valid conclusions can be made about which configuration yields the best performance unless the operating parameters are re-optimized for each new geometric configuration tested. Therefore, in this study, the performance of each configuration at its optimum operating conditions will be determined and compared for a

4.5 Operating Parameters

c) The level of superheat exiting the evaporator,

d) The amount of sub-cool exiting the condenser, and

4.6 Geometric Parameters

b) The tube spacing,

c) The number of refrigerant parallel flow circuits,

CHAPTER V

Analysis of the Existing System (A*TR)

The primary focus of this study is the optimization of the condenser configuration. However, some assumptions about the parameters of the complete air-conditioning system must be made. Air-conditioning systems are characterized by their cooling capacity at 95° F ambient temperature. It is also customary in most residential air-conditioning applications to employ an evaporator that has a 45 ° F saturation temperature. At this temperature, humidity control is maintained by removing sufficient water vapor from the cooled air. Therefore the evaporator saturation temperature is fixed at 45° F in this study.

Using Coil_PC and IPM:

Coil_PC is designed to be a convenient method of analyzing the performance of a wide variety of fin-tube, refrigerant evaporator and condenser and coolant (brine) coils. The program provides a graphical user interface for you to enter data and display your analysis results. The actual coil simulations are performed using rigorous, incremental, tube-by-tube routines. A "knowledge base" of best-practice expertise has been built into the program to help guide you through the program input, and to provide assessments of your coil design.

Coil_PC is organized as a tab sheet comprising a series of both input and results tabs. We will use the input tabs to fill in the detailed geometry, operating conditions, and circuiting for your coil. These tabs are laid out in a roughly sequential order, with later input often depending on earlier values you entered.

The overall Integrated Product Modeling (IPM) program consists of three major parts: User Interface, Solver and Detailed Models. Each part above is a separate executable program; note that there can be more than one detailed model also.

5.3 Detailed Models:

Figure 5.2 Basic Construction on IPM

CHAPTER VI

OPTIMIZATION OF OPERATING PARAMETERS

6.1 Optimization

1) the air velocity over the condenser i.e. CFM

2) The refrigerant charge measured by the sub-cool in the condenser at 95° F ambient temperature.

6.2 Effects of Air Velocity, Ambient Temperature

For a fixed amount of sub-cool at 95° F ambient temperature, there is always an air velocity that yields the maximum capacity. Since the capacity varies so little with air velocity in the optimum range, it is difficult to determine the exact optimum velocity for each sub-cool within an accuracy of more than ± 0.1 ft/s.

Reason:

This phenomenon can be explained by an analysis of the effects of ambient temperature on the Condensing temperature and pressure, the compressor power, and the evaporator cooling capacity. As the ambient temperature decreases, the saturation pressure in the condenser also decreases. Therefore, the pressure rise in the compressor decreases. As a result, the compressor requires less power, and hence, the capacity increases. Furthermore, as the ambient temperature decreases, the condensing temperature decreases. Thus, the enthalpy of the refrigerant entering the evaporator is reduced. The decrease in the enthalpy of the refrigerant entering the evaporator that is produced by the decrease in the ambient temperature causes the evaporator cooling capacity to increase. This decrease in the enthalpy of the refrigerant entering the evaporator also causes a reduction of the mass flow rate of refrigerant required to maintain the evaporator cooling capacity. Hence, the amount of compressor work is decreased. Therefore, the ultimate result of decreasing the ambient temperature is an increase in the capacity of the system. Figure 7-5 shows how evaporator capacity varies with ambient temperature. For the reasons mentioned above, the figure shows that as the ambient temperature decreases, the evaporator capacity increases.

But, unfortunately, this trend is the opposite of the trend in the residential cooling requirements, which increase with ambient temperature.

6.3 Effect of Operating Parameters on System Cost

CHAPTER VII

OPTIMIZATION OF GEOMETRIC DESIGN PARAMETERS FOR PRODUCT A*

7.1 CONDENSER

1 The number of rows,

2 The number of circuit,

7.1.1 Varying the Number of Rows and circuits of Condenser coil

Table 7.1: Fixed parameters for Varying Number of Rows

Figure 7.1: Capacity vs. Number of Rows

Result

On generalizing the graph we can say that, on continuing to increase the number of rows of tubes also further increases the heat transfer area. Hence, intuitively we can assume that the capacity would also continue to increase.

7.1.2 Varying the Number circuits of Condenser coil

Figure 7.3: Capacity vs. Number of circuits

Now since we have some optimized circuit that can be used in to produce a capacity of approx. 70,000 but/hr, so to make it more optimized and to get to know the effect of the fin pitch and tube diameter we will be doing again some further analysis

7.1.3 Varying Fin density:

Figure 7.5: Effect of Fin density on the Capacity

Coil_Pc Analysis:

7.1.4 Varying Tube Diameter:

So the next geometric design parameter is tube diameter. The other fixed parameters are

Figure 7.6: Effect of Tube Diameter vs Capacity

7.2 EVAPORATOR

Since evaporator is the indoor unit there is very limited scope in changing its geometric dimensions. Also on the software analysis of the existing unit of A* TR, it was found that it is already very optimized in terms of capacity and air flow velocity. The software analysis of the evaporator of the existing design is as follows:

7.3 CONDENSER FAN

7.4 COMPRESSOR

7.5 FAN MOTOR

As we are required to change the no. of fans, it becomes imperative to analysis the load as well the performance of the fan motor, especially of the condenser unit. We can increase the RPM in place of increasing the fan diameter for getting higher CFM. In this case the cost increment is lesser and hence the avenue can be explore. For detail of the existing procedure in motor manufacturing see APPENDIX B

7.6 INTEGRATED ANALYSIS ON SOFTWARE TOOL (IPM)

Till now, we have already done the optimization of the each individual part. But we can’t know that on integration of these parts how they work in coordination with each other. So for this we use IPM analysis on the best optimized parts to find out the best possible energy efficiency ratio i.e. EER

CHAPTER VIII

COST REDUCTION OF PRODUCT A*TR

8.1 Objective

1) To do a benchmarking of the existing products with other companies and

2) To develop a new product (D) of improved capacity (approx. 5.5 TR) from the existing product A* by reducing its manufacturing cost by 20%

8.2 Procedure and Planning

8.3 Benchmarking

We found our indoor unit is leading in comparison to other competitor in all respect, but outdoor unit need to be restructure again to save more cost, as it is found that some companies have more compact outdoor unit. Thus we fix our aim to reduce the cost of outdoor unit of product A*TR by 20%.

8.4 Principle: For designing new product of D*TR from A*TR

After predicting the various parameters, now we first simulate it on the coil_pc to estimate the capacity of the new model of D*TR CDU unit. This simulation can also be taken as the validation of our principal.

Coil_pc analysis:

IPM analysis:

On using the simulation part of this, our EER comes out to be 12 btu/hr/watt. Thus this gives us an idea that we are proceeding in right direction and there are much more probable chances that we will be able to reach our aim.

8.6 Drawings and Prototype formation

8.7 Experimentation

8.8 Difficulties & Solutions:

Problems

The hurdles that arouse during the course of this may be summarized as follows

3. Low capacity or EER:

If after all the optimization on the condenser, we couldn’t get be able to get the required capacity then we should over the optimization of the evaporator coil. Also we can play with the dimensions of the indoor unit, but there is much less scope left in it, because then on one way it increases the size of indoor unit and on other way it increases the sheet metal and costs, both are not feasible

CHAPTER IX

CONCLUSIONS AND FUTURE SCOPE

9.1 Conclusions

When packaging and space constraints are not present, the condenser configuration with the largest frontal area possible yields the best system performance, When typical volume and space constraints are imposed, condensers employing 3 rows of tubes yield the best performance. Contrary to intuition, increasing the number of rows to 4 actually increases the material cost of the coil and decreases the system performance when space constraints are imposed.

 For all geometric configurations investigated, as the ambient temperature decreases, the sub-cool at 95 °F ambient temperature that is needed to produce the highest COP increases. If the material cost of the condenser must be reduced, decreasing the fin density from the base configuration value of 13 fins per inch to 17 fins per inch produces a smaller increase in operating cost than decreasing either the number of rows or the frontal area.

9.2 Future scope

APPENDIX A

These fan laws are the empirical laws giving quite accurate idea about the geometrically similar fans. The important parameters involved are:

N = RPM of fan

Law 1:

When only N changes and d & D remains constant

Q α N

P α N²

P α D²

W α D⁵

Law 5:

Variable N and constant P, system parameters, size (D)

Variable N and constant mass flow rate (M), system size (D)

Q α N

APPENDIX B

We visited the PICL (India) Private Limited at Sector-6, Faridabad and were shown the factory by Mr. Mahesh Sharma, Sr. Engineer Design. The R & D department of PICL does the following test to check the quality and reliability of their motors.

a) General construction

a) General construction

Here the physical dimensions of the motor are noted. Apart from these, the functionality of the motor is also analyzed. Thus they test:

• Rated voltage and frequency

• No load current

• Full load performance at rated voltage and frequency

• Full load current

• Break-away starting current

• Test for full load performance

• Leakage current test at 1.1 times rated voltage

• High voltage test at 1.5 KV

APPENDIX C

1. Capacity Rating Test Conditions (also called Standard Ambient Test):

Room air temperature

Wet bulb 30 deg C

Test voltage Rated

Wet Bulb 24 deg C

Outside air temperature

3. Freeze-Up Test Conditions:

Room air temperature

Wet bulb 16 deg C

Test voltage Rated

Wet Bulb 16 deg C

Outside air temperature

5. Discharge Gas Temp. Limit:

Compressor Application criteria:

Dry bulb 50 deg C

Test voltage Rated

Room air temperature

Dry bulb 35 deg C

Test frequency Rated

The unit is operated for two hours.

Outdoor Dry bulb 50 deg C

Rated frequency 50 Hz

Room air temperature

Dry bulb 27 deg C

Test frequency Rated

Max Fan speed