title of presentation enhancement of the coefficient of performance in air conditioning systems by...

Title of Presentation

ENHANCEMENT OF THE COEFFICIENT OF PERFORMANCE IN AIR CONDITIONING SYSTEMS BY

UTILIZING FREE COOLING

A. Al-Salaymeh1, M. Al-Salaymeh2, M. Rabah3, M. Abdelkader1

1Mech. Eng. Dept., University of Jordan, Amman, Jordan2Jordan Telecommunication Company, Zarka, Jordan

3Mech. Eng. Dept., Al-Balqa Applied University, Amman, Jordan

1

2nd International Conference on Thermal Engineering Theory and ApplicationsJanuary 3 - 6, 2006, Al Ain, United Arab Emirates

2nd ICTEA, January 3 - 6, 2006, Al Ain, UAE

Contents of Presentation 2

INTRODUCTION

BASIC DEFINITIONS

ELEMENTS OF REFRIGERATION AND AIR CONDITIONING SYSTEMS

COMPRESSORS

REFRIGERANT AND REFRIGERANT FLOW CONTROL

FREE COOLING

ECONOMIC STUDY OF USING FREE COOLING

CONCLUSIONS


Introduction 3

All sources of energy may be grouped into two general categories:

Income energy, which is the energy reaching the earth from outer space,

Capital energy, which is the energy that already exists on or within the earth.

The utilization of income energy sources is very attractive because they are nondepletable sources of energy and they are relatively pollution free.

Jordan is relatively poor in conventional resources and is basically a non-oil-producing country, i.e. about 95% of its needs being supplied from abroad as crude oil and refined products.

It is therefore unlikely that any future energy scenario for Jordan will not include a significant proportion of its energy coming from Renewable Energy.

It is clear that the government’s plan requires consideration of the increased energy demands of the country and the undertaking of research and development efforts towards solutions of current problems.


Energy Policy in Jordan 4

The energy demand in Jordan has doubled during the last 20 years, and is expected to continue at the same rate, or even higher.

All recent energy forecast scenarios have shown that national energy consumption might double between 2015 and 2020.

Such a rapid increasing demand is due to the high growth rate of the population and the expansion of economical activities in various fields.

By high oil prices, the government is undertaking new measures to improve the situation in the energy sector by formulating and implementing an adjustment plan.

The demand for primary energy in Jordan is 4.8 million tons of oil equivalents (toe), showing a 3% annual growth

The primary energy consumption that was required for electricity generation in 2000 was equivalent to 1.8 million toe.

The average energy consumption per inhabitant is 970 kg oil equivalent.

It is predicted that electricity generation of Jordan will be around 12500 and 15000 GWh in 2010 and 2015, respectively.


5Existing Knowledge & Aim of the Work

The share of solar energy in the total energy mix in Jordan is estimated to be around 1.7% during the year 2002.

The expected share of solar energy in the total energy mix in the year 2007 is estimated to be around 2.1%.

All the above-mentioned attempts to ensure Jordan’s energy supply do not eliminate the need to search for new energy sources in the country.

In order to reduce dependence on the imported oil, Jordan has pursued programs for promoting solar energy involving systematic monitoring and assessment of technological developments combined with the implementation of appropriate technologies, demonstrations and pilot projects.

Free cooling technique in air conditioning system can be utilized to save the energy consumption.

The present work shows the economics study of utilizing free cooling in air conditioning system.


Elements of Air Conditioning 6


Phases in the Cooling Circuit 7

•Compressor makes up the pressure in the discharge line to the condenser coil.

• Due to the cooling effect of the air flow across the condenser the refrigerant vapour will condense to liquid form and heat will be released to the condenser air flow.

• The refrigerant liquid will run into the receiver, which the liquid line to the thermostatic valve, always will be full of refrigerant.

• The filter dryer obtain impurities and humidity.

• The solenoid valve is operating ON/OFF and is an important part in the “Pump down” system.

• The thermostatic expansion valve is located just before the evaporator. The valve releases sufficient amount of refrigerant to the give a little superheat of 4-6C ensuring that all liquid has evaporated.

• The evaporation of refrigerant takes place at low pressure in the evaporator and because the refrigerant has a low boiling temperature, the evaporation process needs heat energy. Heat is taken from the air passing through the evaporator coil, the result will be that the air flow is cooled.


Free Cooling (1) 8

Free cooling take place when the external ambient air temperature is less than the indoor air temperature

Air conditioning systems either provide supply air using:

A mixture of outside air and recirculated (return) air from the shiltter room.

100% outside air systems which are generally used in the cases of hospitals, densely occupied areas such as theatres etc.

Free cooling may be used with mixed outside air and recirculation systems by the use of modulating dampers.

Dampers are provided on the outside air intake ductwork, exhaust air ductwork and the recirculation ductwork.

In the event of cool outside air the quantity of outside air is increased and the quantity of recalculated air is reduced to provide the required supply air temperature. In this way cooling by means of refrigeration equipment is avoided altogether at certain times of year and often at night times.


Free Cooling (1) 9

During cool weather, the outside ambient temperature can help save energy in Air conditioning systems.

The low temperature of the cooling ambient air supply enables free cooling of computer rooms.

Free cooling can be used to save energy whenever the outside wet-bulb temperature drops below the required cooling air set-point.

This energy-efficiency measure can save enough compressor electric power to pay for damper installation costs in less than 2 years.

When the outside air temperature is higher than the room temperature in Summer the dampers will modulate to the minimum outside air position to keep the load on the refrigeration equipment to a minimum.

The free cooling version has a motorized damper that conducts the two flows of internal and external air. When the damper is open it takes the air necessary for cooling directly from the exterior, excluding compressor operation as shown in Figure.


Principle Operation 10

Free cooling offFree cooling on


Economic Study of Using Free Cooling

11

The air conditioning system (small shiltter) uses “free” cooling techniques to reduce energy costs.

COP which is the ratio of cooling energy provided divided by the amount of energy used to run the refrigeration plant, has typical values between 3 and 5.

The 4 ton cooling load in JTC buildings represents about 13.69 kW of cooling load, which is effectively provided with about 3.75 of electrical consumption for a COP of 3.65.

However there are periods of the year where (in the case of JTC cooling ambient temperature can be utilized to provide nearly free cooling (COP > 90 – where the only energy consumption is from the use of evaporative fans.

The compressor of A/C is shut off during this period, thereby saving energy

The compressor of A/C can be shut down form 1 to as may as 4 months a year (from November until February).


Case Study 12

Small equipment room containing telecommunication racks, file servers or a midrange computer and it needs cooling. The hardware manufacturer recommends controlled conditions of 22C 2C and a relative humidity of 50% 5%.

Usually, a package air conditioning system is used in order to cool the room to the desired condition.

The cost of electrical energy is increasing because of the increasing prices of the oil and the high demand on the oil and the shortest resources of energy.

This fact was the main motivation for many researchers and scientific people to look for a method for saving energy. The new scientific work was resulted developing the free cooling technology in air conditioning system.

This method is based on using the outside air when the ambient temperature decreases below the desired inside temperature. Since the equipment room contains some telecommunication devices such as servers and computers, its temperature is usually high.


Technical Data (1) 13

Model

Evaporator DataAMBIENT TEMEATURE F

75 85 95 100 105 115

Air Flow Rate

On CoilTotal

Capacity

Sensible Capacit

y

Total Capacity

Sensible Capacity

Total Capacity

Sensible Capacity

Total Capacity

Sensible Capacity

Total Capacity

Sensible Capacity

Total Capacity

Sensible CapacityD

BWB

CFM F F MBH MBH MBH MBH MBH MBH MBH MBH MBH MBH MBH MBH

PWM 20

750

76 63 22.1 16.0 21.1 15.6 20.1 15.2 19.6 15.0 19.2 14.8 18.1 14.4

78 65 22.9 15.9 21.9 15.5 20.9 15.1 20.4 14.9 19.9 14.8 18.7 14.3

80 67 23.9 15.9 23.0 15.6 22.0 15.2 21.4 15.0 20.9 14.8 19.8 14.4

PWM 25

900

76 63 26.2 19.2 25.1 18.8 23.9 18.3 23.2 18.0 22.7 17.8 21.4 17.3

78 65 27.1 19.1 25.9 18.7 24.7 18.2 24.1 18.0 23.5 17.8 22.2 17.3

80 67 28.3 19.2 27.1 18.7 25.9 18.3 25.3 18.0 24.7 17.8 23.4 17.3

PWM 33

1060

76 63 34.2 25.0 32.5 24.2 30.7 23.5 29.7 23.1 28.8 22.7 26.8 21.9

78 65 35.4 24.8 33.6 24.1 31.8 23.4 30.9 23.1 30.0 22.7 27.9 21.9

80 67 37.1 24.9 35.3 24.2 33.4 23.5 23.5 23.1 31.5 22.8 29.4 22.0

PWM 42

1600

76 63 44.4 31.5 42.3 30.6 40.1 29.7 38.8 29.2 37.6 28.7 35.1 27.7

78 65 45.9 31.3 43.9 30.5 41.6 29.6 40.3 29.1 39.1 28.7 36.5 27.7

80 67 48.2 31.4 46.0 30.5 43.6 29.7 24.4 29.2 41.1 28.8 38.4 27.8

PWM 48

2000

76 63 49.4 36.1 47.3 35.2 45.0 34.3 44.0 33.9 42.8 33.5 40.6 32.6

78 65 51.1 35.9 48.9 35.1 46.7 34.2 45.6 33.8 44.5 33.4 42.3 32.6

80 67 53.4 35.9 51.1 35.1 48.9 34.3 47.9 33.9 46.7 33.5 44.4 32.7

PWM 58

2100

76 63 57.6 43.7 55.2 55.2 52.8 41.7 51.5 41.2 50.2 40.7 47.7 39.8

78 65 59.6 43.5 57.1 57.1 54.6 41.6 53.4 41.1 52.1 40.6 49.5 39.6

80 67 62.3 43.5 59.8 59.8 57.4 41.7 56.0 41.2 54.6 40.7 51.8 39.7



PWM Model

Power Supply

Compressor CFM EFM

Nominal Motor Power

HP(Kw)

No.

LRA(Each

)(AMP

)

RLA(Each

)(AMP

)

Motor (Kw)

No.

FLA(Each

)(AMP

)

Motor (Kw)

No.

FLA(Each

)(AMP

)

PWM 20

220-240 V/1 ph/50 Hz

2(1.49) 1 46 11.9 0.165 1 0.8 0.147 1 1.7

PWM 25 2.5(1.87) 1 58 15 0.165 1 0.8 0.147 1 1.7

PWM 33 3(2.24) 1 87 19.1 0.165 1 0.8 0.147 1 1.7

PWM 42

280-420 V/3 ph/50 Hz

3.5(2.61) 1 42 8.2 0.245 1 1.1 0.147 1 1.7

PWM 48 4.5(3.36) 1 55 10.4 0.245 1 1.1 0.147 1 1.7

PWM 58 5(3.73) 1 65 9.6 0.245 1 1.1 0.147 2 1.7



The electrical data for power supply are:1.Compressor: Nominal Motor Power = 4.5 HP = 3.36 kW.2.Condenser for Motor = 0.245 kW.3.Evaporator for Motor = 0.147 kW.

Total electrical Input power = Motor Power for Compressor + Condenser + Evaporator

= 3.36 + 0.245 + 0.147 = 3.75 KW.

The Coefficient of Performance = COP = 13.69/3.75 = 3.65


Room Volume = 3.0 m 2.5 m 2.5 m

Air flow rate for evaporator = 2000 cfm.

Cooling capacity of air conditioning system = 4.0 ton cooling load.

The outside ambient temperature at Zarka city was taken as 95F (35C)

Ambient Temperature 16

0

5

10

15

20

25

30

35

40

Jan.

Feb.

Mar

chApr

ilM

ayJu

ne July

Augus

t

Sept.

Oct.Nov

.Dec

.

Month

Tem

pe

ratu

re C

Tmin °CTmax °C

A comparison between the monthly average of minimum and maximum temperature values of Zarka city as a function of months


0

5

10

15

20

25

30

35

40

0 2 4 6 8 10 12

Month

Tem

per

atu

re C

Tmin °C

Tmax °C

The Cost of Operating A/C Without Free Cooling

17

0

5

10

15

20

25

Jan.

Feb.

Mar

chApr

ilM

ayJu

ne July

Augus

t

Sept.

Oct.Nov

.Dec

.

Month

No

. o

f O

pe

rati

ng

Ho

urs

Compressor

• Cost of 1 kWh electricity = 0.05 JD

• Number of operating hours for A/C in April day is 12 hours.

•Total number of operating hours in April for A/C is 30 * 12 = 360 hours

• The cost of 360 hours per 1 kWh power = 360 * 0.05 = 18 JD

• Since our selected A/C has a total input electrical power of 3.75 kW,

Cost in April month = 30 days * 12 hours * 0.05 JD * 3.75 kW= 67.5 JD

0

20

40

60

80

100

120

140

Jan.

Feb.

Mar

chApr

ilM

ayJu

ne July

Augus

t

Sept.

Oct.Nov

.Dec

.

Month

Co

st

(JD

)

Compressor Cost


Cost of Operating Evaporator Fan Without Free Cooling

18

Normally, the air conditioning unit in JTC is permanently operated and therefore the evaporator fan will continue work during the time which the compressor is not working.

The electrical power for evaporator motor = 0.147 kW.The evaporator fan will be worked 12 hours more in April month,

therefore:Cost in April for evaporator fan = 30 days* 12 hours*0.05 JD*0.147

kW = 2.64 JD

0

2

4

6

8

10

12

14

16

18

20

Jan.

Feb.

Mar

chApr

ilM

ayJu

ne July

Augus

t

Sept.

Oct.Nov

.Dec

.

Month

No

. of

Op

era

tin

g H

ou

rs

Evaporator Fan

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Jan. Feb. March April May June July August Sept. Oct. Nov. Dec.Month

Co

st

(JD

)Evaporator Cost


Total Cost of A/C Without Free Cooling

19

0

20

40

60

80

100

120

140

Jan.

Feb.

Mar

chApr

ilM

ayJu

ne July

Augus

t

Sept.

Oct.Nov

.Dec

.

Month

Co

st (

JD)

Evaporator CostCompressor CostTotal Cost

Total cost of A/C in April month that operates 24 hours per day (12 hours complete operation and 12 hours evaporator fan only) is: 67.5+2.64 = 70.14 JD

Total yearly cost = Sum of total electricity cost during 12 months = 948.5 JD


•Total electricity cost of the selected A/C in addition to the cost of the evaporator fan at different months.

Cost of Operating A/C with Free Cooling

20

No. of operating hours for A/C in April in the presence of free cooling is 5 hrs/day

Total number of operating hours in April for A/C is 30 * 5 = 150 hours

The cost of 360 hours per 1 kWh power = 150 * 0.05 = 7.5 JD

Since our selected A/C has a total input electrical power of 3.75 kW, therefore the total cost of operating such a unit during April is

Cost in April month = 30 days * 5 hours * 0.05 JD * 3.75 kW= 28.125 JD

0

2

4

6

8

10

12

14

16

Jan.

Feb.

Mar

chApr

ilM

ayJu

ne July

Augus

t

Sept.

Oct.Nov

.Dec

.

Month

No

. of

Op

erat

ing

Ho

urs

Compressor

0

10

20

30

40

50

60

70

80

90

100

Jan.

Feb.

Mar

chApr

ilM

ayJu

ne July

Augus

t

Sept.

Oct.Nov

.Dec

.

Month

Co

st

(JD

)

Compressor Cost


Cost of Operating Evaporator Fan with Free Cooling

21

The electrical power for evaporator motor = 0.147 kW.

The evaporator fan will be worked 19 hours more in April month, therefore

Cost in April for evaporator fan = 30 days * 19 hours * 0.05 JD * 0.147 kW = 4.19 JD

0

5

10

15

20

25

30

Jan.

Feb.

Mar

chApr

ilM

ayJu

ne July

Augus

t

Sept.

Oct.Nov

.Dec

.

Month

No

. of

Op

era

tin

g H

ou

rs

Evaporator Fan

0

1

2

3

4

5

6

Jan. Feb. March April May June July August Sept. Oct. Nov. Dec.Month

Co

st

(JD

)Evaporator Cost


Total Cost of A/C without Free Cooling

22

The total cost of A/C in April month that operates 24 hours per day (5 hours complete operation and 19 hours evaporator fan only) is 28.125 JD + 4.19 JD = 32.135 JD

Total yearly cost = Sum of total electricity cost during 12 months = 543.92 JD

0

10

20

30

40

50

60

70

80

90

100

Jan.

Feb.

Mar

chApr

ilM

ayJu

ne July

Augus

t

Sept.

Oct.Nov

.Dec

.

Month

Co

st (

JD)

Evaporator Cost

Compressor Cost

Total Cost


Total electricity cost of the selected A/C in addition to the cost of the evaporator fan at different months

Total Cost With & Without Free Cooling

23

Total cost of operating A/C without free cooling = 948.50 JD/ year.

Total cost of operating A/C unit with free cooling = 543.92 JD/year.

The difference in the cost = 948.50 – 543.92 = 404.58 JD.

% of money saving = 404.85/948.50 = 42.6%

This result means that 42.6% from the total cost of electricity can be saved each year in the case of using free cooling technique.

The capital cost of the A/C system with dampers for free cooling is higher than the normal A/C by about 500 JD.

This means that the difference in the Capital Cost can be recovered after one year from operation because the running cost of operating A/C with free cooling is 400-500 JD less than the normal A/C



24

0

20

40

60

80

100

120

140

Jan.

Feb.

Mar

chApr

ilM

ayJu

ne July

Augus

t

Sept.

Oct.Nov

.Dec

.

Month

Co

st (

JD)

Total Cost with Free Cooling

Total Cost without Free Cooling

A comparison between the total electricity cost for operating air conditioning unit in the case of presence or absence of free cooling at the

desired location and the required cooling capacity.


0

20

40

60

80

100

120

140

0 2 4 6 8 10 12

Month

Co

st

(JD

)

Total Cost with Free Cooling

Total Cost without Free Cooling

Poly. (Total Cost with FreeCooling)Poly. (Total Cost without FreeCooling)


25

• The Coefficient of Performance (COP) can be reached a very high value in the case of free cooling.

• As it is known, the coefficient of performance is defined as the ratio between the output cooling load and input electrical power.

• The output cooling load is the same in the two cases which are the presence of free cooling air conditioning unit and in the absence of free cooling.

• But, the electrical input power is reduced in the case of free cooling and the input power is only the power needed for evaporator fan.

• Therefore, the calculated value of the coefficient of performance in the presence of free cooling is:The Coefficient of Performance = COP = 13.69/0.147 = 93.13 While in the absence of free cooling

The Coefficient of Performance = COP = 13.69/3.75 = 3.65


Conclusions 26

• The main purpose of this project to study the utilizing of free cooling in the A/C system especially for the rooms which contains some heat generating sources and they needs to be cooled all days around the year. •During cool weather, the outside ambient temperature can help save energy in A/C systems. • The 4 ton cooling load in JTC buildings represents about 13.69 kW of cooling load, which is effectively provided with about 3.75 kW of electrical consumption for a COP of 3.65. • However there are periods of the year where cooling ambient temperature can be utilized to provide nearly free cooling and the COP > 90 – where the only energy consumption is from the use of evaporative fans.• The A/C system uses “free” cooling during cold weather without the requirement to run a compressor. The compressor of A/C is shut off during this period, thereby saving energy. •The cost for damper installation can be recovered in less than two years.


End of presentation 27


Everything should be made as simple as possible, but not simpler. Albert Einstein (1879 - 1955) A theory is something nobody believes, except the person who made it. An experiment is something everybody believes, except the person who made it. Albert Einstein (1879 - 1955)

It is a capital mistake to theorize before one has data. Insensibly one begin to twist facts to suit theories instead of theories suit facts. C. Doyle

Thanks for you attention,

استماعكم لحسن جزيلا شكرا

The Final Conclusion !

title of presentation enhancement of the coefficient of performance in air conditioning systems by...

Documents

energy demand

energy policy

increased energy

capital energy

energy sector

renewable energy

primary energy consumption

total energy mix