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A PROJECT REPORTON

EARTH TUBE AIR COOLER

Submitted By

Ashutosh Tiwari

Pradeep Singh Dhaliwal

Rajendra Singh Rajput

Uday H. Singh

Mukund Kumar

Under the guidance of

Prof. Krishna Shrivastava

Department Of Mechanical Engineering,

SSBTS College ofEngineering & Technology,

Bambhori, Jalgaon. (M.H.)


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SSBTS College of Engineering & Technology

Bambhori, Jalgaon (M.H.)

Department of Mechanical Engineering(20102011)

CERTIFICATEThis is to certify that in project report entitled

EARTH TUBE AIR COOLER

As submitted by

Ashutosh Tiwari

Pradeep Singh Dhaliwal

Rajendra Singh Rajput

Uday H. Singh

Niket ShahTo north maharastra university in partial fulfillment of the degree of

Bachelor of Engg (B.E) under my Supervision and guidance.

Prof. Krishna Srivastava Mr. J. R. Choudhary

(Guide) H.O.D

(Mechanical dept.)

Dr. Rakesh Mowar

(Principal)


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PREFACE

In Final year of Mechanical Engineering every student has undertaken one major project.

While selecting the subject or project, the following characteristics should be kept in mind.

1. It should test the skill attitude and the group range of knowledge of every student.2. It should consider the local, social and industrial people and try to the fulfill it.3. Preference should be given to the student and selection of project should match their

program me performance considering all their ability to works.


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Acknowledgement

It was a great experience to sharpen working of Earth Tube Air Cooler for cooling of air

with practical tool. The little experience of making project in practice was like adding a bit ofsugar to the milk.

We are grateful to our project guide Prof. Krishna Shrivastava, APMED, also a

our head of the Mechanical Department Mr. J. R. Choudhary who has given essential guidance

and personal interest and constructive ideas helped us to get the best work (project) from them

about our project.EARTH TUBE AIR COOLER.

Thanking You,

Yours Sincerely

(PROJECT GROUP)


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CONTENTS

Index of Report

Abstract

NomenclatureChapter - 1 Introduction

1.1 Principle1.2 Application1.3 Scope of project1.4 Organization of reportChapter - 2 Literature Review

2.1 Introductions

2.2 Reference papers

2.3 Climatic & Geo-thermal conditions

2.4 Concluding Remark

Chapter3 Theoretical Analysis and Thermal Calculations

3.1 Introduction

3.2 Assumptions

3.3 Estimate cooling for room

3.4 Calculations for length of pipe (l)

3.5 Thermal network

3.6 Earth soil model

Chapter 4 - Experimental Setup

4.1 Introduction

4.2 Material Selection

4.3 Flow Diagram

4.4 Experimental setup

4.5 Blower selection

4.6 Design Procedure

4.7 Working of model

4.8 Experimentation

4.9 Result to be achieved


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4.10 Maintenance

Chapter5 Practical analysis and Readings

5.1 Readings

5.2 Air temperature at outlet of ETAC & Soil temperature

5.3 Calculations

5.4 Earth Soil model

Chapter6 Conclusions

6.1 Future scope

6.2 Conclusions

References


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NOMENCLATURE

Symbol Description Unit

Q cooling load W

L length of pipe M

Ti inlet air temperature of pipe K

To outlet air temperature of pipe K

Tc average soil temperature K

Tlm log mean temperature K

Tam bulk mean temperature K

Di inner diameter of pipe M

Do outer diameter of pipe M

Ao

outer surface area of pipe m2

Kair thermal conductivity of air W/m-k

Kpipe thermal conductivity of pipe W/m-k

Ha convection coefficient of air W/m2-k

Hw convection coefficient of water W/m2-k

Rfi Fouling factor for inner surface m2k/W

Rfo fouling factor for outer surface m2k/W

Uo Overall heat transfer coefficient on outer tube surface W/m2k

u velocity of air in pipe m/sec

Cp specific heat of air J/kg-k

kinematic viscosity m2/s

Pr Prandtl number

Rc Reynolds number

Nu Nusselt number


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ABSTRACT

Earth-tube air cooler is a subterranean cooling system that utilizes ground temperature for

pre-cooling or pre-heating ventilation air in summer. Earth tubes (earth tubing) are, in a word,

low-tech, sustainable, non-electric, zero-energy passive geothermal solar heating and solar

cooling systems. Earth tubing utilizes conventional, thin wall plastic 'sewer' pipe to passively

(zero-energy) pre-heat your home's fresh air intake. Filtered fresh air enters a series of non-

porous pipes embedded in the soil, absorbing energy from the surrounding soil, moderating the

temperature of fresh air intake. When done correctly, air drafts naturally through your earth tubes

for a truly sustainable, non-electric, zero-energy, passive geothermal system that nicely

supplements a better hub.

The whole sole objective to design the earth tube air cooler is to provide pre-cooling upto

1TR to 5TR which can be used for domestic cooling purpose. We are building the system on the

basis of Jalgaon climatic conditions in summer. In this project the pre-cooling of air up to the

earth temperature. The other factors like Relative humidity, specific humidity, enthalpy, entropy

is not main focus. But it is observed that the due to cooling the humidity decreases.

Earth tubes are often a viable and economical alternative or supplement to

conventional central Air conditioning systems since there are no compressors, chemicals or

burners. Only blowers are required.

The ETHE in India is used in the agricultural and horticultural purposes, ETHE are

bulky. The objective of this project is to bring the use of ETHE up to domestic level. To reduce

the size of the earth tube, making it compact for use in the domestic household. We are building

a model description of the earth tube for cooling a small chamber.

The same technology is frequently used to preheat the air in cold regions.
http://en.wikipedia.org/wiki/Central_heatinghttp://en.wikipedia.org/wiki/Air_conditioninghttp://en.wikipedia.org/wiki/Air_conditioninghttp://en.wikipedia.org/wiki/Central_heating


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CHAPTER 1: INTRODUCTION

The "Earth-Tube Air Cooler (ETAC)" technology is a low cost solution to reduce the

cost of heating and cooling your home. By using the Earth as a medium anyone can heat and

cool their house for less. Unlike other cooling machinery, air tubes don't require compressors,

pumps, Storage tanks, coils, heat exchangers, complex plumbing, or all the problems inherent in

a complex equipment/technology in intensive heating and cooling system. Properly installed air

tubes don't have any moving parts. They can't break. The only technology required is a fan to

move the air through the tubes and into the house. Earth tubes are relatively inexpensive to

install and are inexpensive to operate. Specific aim of these to get cool air without using any

refrigerant & mechanical ventilation system & making it an alternative product for desert cooler

also making it a hub for eco friendly pollution free zone.

In the late 1970's and early 1980's Earth air tubes gained a lot of popularity as an aid to

conventional air conditioning and heating. Mathematical models of ETHE have also been

developed. There has also been some work in India. Sharan in his work installed an ETHE based

system to cool part of a guesthouse and at Ahmadabad Zoological Garden. Tata Energy Research

Institute installed ETHE to cool rooms in its training center near Delhi. Many earth tube systems

are designed for cooling, either in Western Europe (Germany, Switzerland) or in warmer places

such as India, particularly for greenhouse applications. Earth tube systems are reported to be

gaining acceptance in some Northern European countries, particularly Sweden and Finland.

ETHE is used to condition the air in livestock buildings. It is used in North America and

Europe to cool and heat greenhouses. Mathematical models of ETHE have also been developed

(Puri 1985; Goswami and Dhaliwal 1985). Baxter's facility at Knoxville, Tennessee (USA) is a

single pass earth-tube heat exchanger 64-m long, 15-cm diameter; made of 18- gauge spirally

corrugated galvanized metal. The tube is buried at 1.8-m depth, and is elaborately instrumented

with temperature sensors inside the tube and in soil around it. Air is 4 pumped by a high pressure

industrial blower of about 572 w powers. Instrumentation permits measurement of air

temperature along the tube and in soil around the tube.


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Earth air tube cooler explores the soil temperature below the ground surface to pre-cool

the ventilation air, performance varies with climatic and soil condition of the area. The system

can significantly improve comfort conditions. ETHE is being used based on the temperature

condition for the soil and environment of Jalgaon.

1.1 PRINCIPLE:-The earth tube air cooler work by simply exposing the air we are drawing through the

tubes into the house to the temperature of the soil without actually exposing the air to the soil. As

air travels through the tubes they exchange temperature with the surrounding soil.

The air entering the house will be warmer then the outside air in the winter and cooler

than the outside air in the summer. An Earth air tube system is a one way open-air system.

Outdoor fresh air is drawn into the tubes, cooled (in the summer) by the Earth, and delivered to

the inside of the house via the outlet. This system provides fresh conditioned air to every room in

the house.

Average temperature in this stratum of earth is 27C (the temperature range is from in

24oC to 29oC in winter and summer respectively it is highly suitable for this technology.

Fig No. 1.1 ETHE Project developed in Europe

1.2 APPLICATION:-

Earth tubes are often a viable and economical alternative or supplement to

conventional central heating or air conditioning systems since there are no compressors,

chemicals or burners and only blowers are required to move the air. These are used for either
http://en.wikipedia.org/wiki/Central_heatinghttp://en.wikipedia.org/wiki/Air_conditioninghttp://en.wikipedia.org/wiki/Air_conditioninghttp://en.wikipedia.org/wiki/Central_heating


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partial or full cooling and/or heating of facility ventilation air. Their use can help buildings meet

the German Passive House standards or the North American LEED's (Leadership in Energy and

Environmental Design) Green Building rating system.

Earth-air heat exchangers have been used in agricultural facilities (animal buildings) and

horticultural facilities (greenhouses) in the United States over the past several decades and have

been used in conjunction with solar chimneys in hot arid areas for thousands of years, probably

beginning in the Persian Empire. Implementation of these systems in Austria, Denmark,

Germany, and India has become fairly common since the mid-1990s, and is slowly being

adopted into North America.

1.3SCOPE OF WORK:-The economics are too positive for cooling applications, because in some climates earth

tubes enable the user to dispense with a dedicated air-conditioning system. The earth tubes are

used for cooling in the summer. The research papers shows results that earth tubes can provide

between 30% and 100% of cooling needs. In heating mode earth tubes help prevent freezing on

the intake of heat recovery ventilators. Coefficients of Performance (COPs) around 30 for pre

heating they arecalculated by dividing the energy transfer the earth tubes by the incremental fan

power required to push the air through them.COP for cooling 1.5 can be calculated by heat

transferred to the air divided by fan power. The COP 1.5 with such less investment is reasonableto attract the researches towards it.
http://en.wikipedia.org/wiki/Germanyhttp://en.wikipedia.org/wiki/Passive_Househttp://en.wikipedia.org/wiki/Leadership_in_Energy_and_Environmental_Designhttp://en.wikipedia.org/wiki/Leadership_in_Energy_and_Environmental_Designhttp://en.wikipedia.org/wiki/Passive_Househttp://en.wikipedia.org/wiki/Germany


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CHAPTER 2: LITERATURE REVIEW

2.1 INTRODUCTION

This chapter contains the literature review to brief the objective of our work. We have

collected the detail literature with a view to develop this project focusing on cooling of air using

earth stable temperature. The basic technology and principle are based on heat transfer. But the

decision regarding sizes of the project was complex. The review has covered various references

and assumptions which can be used for the theoretical analysis and thermal design of the project.

2.2 REFERENCE PAPERS

Girja Sharan(1): This paper published in year 2002,System design in this paper delivers air at

44.4 m

3

/min. It consists of two 20 cm diameter MS pipes placed in parallel at two meter depth inthe moat near the dwelling. Pipes are 27 m long each and are separated horizontally by 1.5 m.

Air is moved by a 1.2 KW blower. This system cools the ambient air in hot summer by about

50C and warms the cold air in winter by about 10C. System was designed at the zoo because it

does not increase humidity in the as a desert cooler does. This paper also describes the working

of ETHE as dual mode conditioner-cooling in summer and warming in winter.

Fig No. a. model presented by Girija Sharan.

Fig. a


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Didier kerpel(2): Tubes are put into the ground, through which air is drawn. Because of the high

thermal inertia of the soil, the temperature fluctuations at the ground surface exposed to the

exterior climate are damped deeper in the ground. Further a time lag occurs between the

temperature fluctuations in the ground and at the surface. Therefore at a sufficient depth the

ground temperature is lower than the outside air temperature in summer and higher in winter.

When fresh ventilation air is drawn through the EAHX the air is thus cooled in summer and

heated in winter. In combination with other passive systems and good thermal design of the

building, the EAHX can be used to avoid air-conditioning units in buildings, which results in a

major reduction in electricity consumption of a building.

Fig no b model presented by Didier kerpel

Janssens, M. Steeman, J. Desmedt, H. Hoes, M. De Paepe(3):

Earth-air heat exchangers are a possible technique to reduce energy consumption for

heating and cooling in buildings. Tubes are put into the ground, through which ventilation air isdrawn. Thus ETHE can cool or heat the ventilation air, using the soil as a heat source or sink.

Their performance depends on the air flow rate, convective heat transfer at the tube surface,

depth, dimensions and number of pipes and soil properties. Only a moderate climate having a

large temperature difference between summer and winter is suited for ETHE. As the heat

exchanger has a good peak performance but a limited seasonal capacity, it is an interesting

Fig. b


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technique in combination with other energy saving measures. For instance, the ETHE may

prevent frosting of a conventional air-air heat exchanger during cold weather, thus increasing the

number of operation hours of the heat exchanger combination. Furthermore, in combination with

other low-energy cooling techniques (eg night cooling) and good thermal building design, the

ETHE may eliminate the need for an air conditioning system.

Larry Larson (4): The "Earth Coupled Air Tube" technology is a low cost solution to

reduce the cost of heating and cooling your home. By using the Earth as a heat sink anyone can

heat and cool their house for less. Unlike the ground loop heat pump, air tubes don't require deep

wells, compressors, pumps, Storage tanks, coils, heat exchangers, complex plumbing, or all the

problems inherent in a complex equipment/technology intensive heating and cooling system.

Properly installed air tubes don't have any moving parts. They can't break. The only technology

required is a fan to move the air through the tubes and into the house. Earth tubes are relatively

inexpensive to install and are inexpensive to operate.

Abdullahi Ahmed and Kassim Gidado (5):The combination of high ambient temperatures and

solar radiation in Tropical climate causes thermal discomfort in buildings. Mechanical air-

conditioning systems are used for cooling buildings, with high energy demands to operate and

maintain these systems continuously over long periods of time over the year. With the rapid

increase in population and economic growth of countries in the tropical regions, it is becoming

inevitable that passive and low energy strategies must be used as suitable alternatives for

cooling. Earth-air heat exchanger (EAHX) is a subterranean ventilation system that explores soil

temperature below the ground surface to pre-cool or pre-heat ventilation air, performance varies

with climatic and soil condition of the area. This research has determined the climatic and soil

parameters affecting the thermal performance of EAHX for chosen locations in Nigeria. Thermal

simulations have been carried out using Transient System Simulation Environment (TRNSYS) to

evaluate the cooling energy gain and the reduction of ambient temperature extremes. The results

show that the system can significantly improve comfort conditions and reduce building cooling

loads.


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Kwang Ho Lee , Richard K (6): Strand The utilization of geothermal energy to reduce heating

and cooling needs in buildings has received increasing attention during the last several years. An

earth tube is a long, underground metal or plastic pipe through which air is drawn. As air travels

through the pipe, it gives up or receives some of its heat to/from the surrounding soil and enters

the room as conditioned air during the cooling and heating period.

2.3 CLIMATIC AND GEO-THERMAL CONDITION

The table no. 1 shows the average temperature of soil measured at the depth of 3m from

surface of earth in Jalgaon region. The table shows the details of minimum and maximum

temperature of Jalgaon along with the Relative Humidity and temperature.

Table no. 1 Monthly average soil temperature of Jalgaon.

Month Basic Soil

Temperature

January 24.2C

February 25.2C

March 25.8C

April 26.6C

May 26.6C

June 29.8C

July Not tested

August Not tested

September 28.1C

October 25.6C

November 24.2C

December 24.1C


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Table no. 2 Climatic conditions of Jalgaon.

Month

Mean Daily

Maximum

Temperature

Mean Daily

Minimum

Temperature

Highest Maximum ever

recordedLowest Minimum ever recorded

Relative Humidity

0830* 1730*

c c c Date c Date % %

January 30.4 12.6 35.6 2005 Jan. 1.7 1945 Jan. 7 60 30

March 37.5 18.6 43.9 2005 Mar. 9.4 1948 Mar. 16 41 18

April 40.9 24.1 47.2 2005 Apr. 15.6 1944 Apr. 9 43 18

May 42.5 27.2 47.8 2005 May 22.2 1956 May 31 56 22

June 37.8 26.1 46.1 2005June 21.7 1955 June 17 72 44

July 31.4 23.9 39.4 2005 July 21.1 1938 July 12 86 68

August 31.4 23.5 37.2 2005 Aug. 20.0 1942 Aug. 27 86 68

October 34.1 19.2 38.3 2005 Oct. 10.0 1950 Oct. 30 69 42

November 31.8 14.5 36.5 2005 Nov. 5.6 1950 Nov. 19 64 33

December 29.7 12.3 35.2 2005 Dec 1.7 1937 Dec. 3 65 34

2.4 CONCLUDING REMARK

As results of theoretical and experimental studies, the earth tube model showed a good

agreement as compared with deserts coolers and shows good economics with air conditioners.

Thus we can accept this work for further studies and experimentation.

The various considerations regarding design and thermal design of this system is

available. The literature review has given the details of sizes that diameter of pipe, selection of

material, depth up to which the cooler to be placed, Cooling range, Humidity controls etc.

The depth up to which the cooler to be placed in 3m below the earth. The pipe material is

mild steel even if its conductivity (55w/m.K) is lower than copper (400w/m.k) because the

conductivity of earth (1.5w/m.k) is very less than M.S. Pipe length, air velocity inside pipe and

pipe depth turned out to have more influence on earth tube performance than pipe radius. Thevelocity of air in the room is as per comfort air conditioning (reference no 10).The velocity of air

in the room can be used to select the fan and the velocity of air to be entered in the pipe.


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CHAPTER-3: THEORITICAL ANALYSIS AND THERMAL

CALCULATIONS

3.1 INTRODUCTION

This chapter contains the theoretical analysis and thermal calculations of our project

work. We have some assumptions for calculating the length of pipe and amount of heat transfer

for the cooling purpose. The basic technology and principle are based on heat transfer. But the

decision regarding sizes of the project was complex.

3.2ASSUMPTIONS1. As per domestic purpose we need 1TR to 5TR refrigeration.2. Convection flow inside the pipe is hydro dynamically and thermally developed.3. Soil temperature in the pipe vicinity can be calculated using the soil model discussed

below beyond a particular distance from the center of the pipe (thickness of the annulus).

4. The temperature profile in the pipe vicinity is not affected by the presence of the pipe. Asa result, the pipe surface temperature is uniform in the axial direction.

5. The soil surrounding the pipe is homogeneous and has a constant thermal conductivity.6. Pipe has a uniform cross sectional area in the axial direction.7. Damp soil temperature constant it is 27oC with reference to the table no 1.8. Conductivity of pipe (k) constant throughout.9. Temperature of air varying in axial direction.10.Assume single pass single pipe heat exchanger because the earth is acting like sink

therefore temperature not changes.

11. Flow of air is turbulent and flow is fully developed.

3.3ESTIMATE COOLING FOR ROOM

We are doing the thermal analysis of ETHE for 1TR cooling load for small room of 3x3x3.5 m3.

Inner diameter of pipe = 10cm = 0.1m {Reference no 11}

Outer diameter of pipe = 10.6cm = 0.106m

Comfort requirement in summer {Reference no 9}

Condition of air


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1. Room temperature = 30oC2. Velocity of air in room = 6m/min3. Relative humidity of air inside room(W) = 50%

Selection of pipe {Reference no 10}

Type of pipe Thermal conductivity (W/m-k)

Copper 401

Aluminum 250

Mild steel 55

Galvanized Steel 18

PVC 0.19

Soil conductivity at 300 k {Reference no 10}

Material Conductivity(W/m-k)

Soil 0.52

Clay 1.3

3.4 CALCULATION FOR LENGTH OF PIPE (L):-

Cooling load (Q) = 1TR = 210KJ/min = 3500W (J/s)

Inner Diameter (Di) = 10cm = 0.10m

Outer Diameter (Do) = 10.6cm = 0.106m

Inlet air temperature (Ti) = 45C = 318K

Outlet air temperature (To) = 30C = 303K

Basic soil temperature (Tc) = 27C = 300K

Thermal conductivity of pipe (Kpipe) = 55W/m-k

Convection coefficient of water (hw) = 500w/m2k

Velocity of air in pipe (u) = 8m/s

Bulk mean temp (Tam) = (318+303)/2 = 310.5K

Properties of air at 310.5K

Density () = 1.1264 kg/m3

Specific heat (Cp) = 1.0074 KJ/kg-K

Viscosity () = 16.946x10-6 m2/sec


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Thermal conductivity of air (Ka) = 27.077x10-3

W/m-K

Prandtl number (Pr) = 0.7055

Flow through circular pipe

Reynolds num (Re) = u*Di/ = 8x 0.1/16.946x10-6

= 47208.78

Nusselt number (Nu) = 0.023xRe0.8

Pro.3

= haxDi/Ka

Convectional coefficient of air (ha) = (0.023x ka x Re0.8

x Pr0.3

)/Di

= 0.023x27.077x10-3

x 47208.780.8

x0.70550.3

= 30.76 W/m2-K

Based on the experience of manufacturer and uses the tubular equipment manufacturer

association prepared the tables of fouling factors as a guide in heat transfer calculation.

Fouling factor (Rfo) = 0.0001m2k/w

Fouling factor (Rfi) = 0.00035 m2 k/w

Overall heat transfer coefficient based on outside tube surface can be expressed as

Overall heat transfer coefficient (Uo) = 1/ [{(Do/Di)xhi} + {(Do/Di)xRfi} + {Do*ln

(Do/Di)/2kpipe} + Rfo + 1/hw]

Uo = 1/ {0.0344 + 3.71x10-4

+5.615x10-5

+ 0.0001 + 2x10-3

}

= 27.08 W/m2K

Outer surface area of pipe (Ao) = 3.14xDoxL

Ao = 3.14x0.106xL


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3.5 THERMAL NETWORK


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T1 = 318-300 = 18K

T2 = 303-300 = 3K

Log mean temperature (Tlm) = (T1-T2)/ln (T1/T2)

= 18-3 / ln (18/3) = 8.37K

Q = Uo xAoxTlm

3500 = 27.08 x 3.142 x 0.106 x L x 8.37

L = 46.27m

3.6 EARTH SOIL MODEL

Cooling time = 24 hrs

Amount of heat transferred in 24 hrs (Q) = 1TR = 210x1000x60x24 J

Q = 302.4x106

J

Convection co-efficient of water (hw) = 500 W/m2 k

We know that

Q = [ mw CpwT + mE CpET]

mw = 20% mE

302.4x106 = [ 0.2 x mE x 4200 + mE x 880] x [37.527]

Ti = 45C =

318K

To=30C=

303K

Tc =27C =

300K


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ME = 16744 kg.

Density of soil (soil) = 2050 kg/m3

[reference no 10]

Volume of soil = mass/ density

= 16744/2050

= 8.17 m3

Length of pipe = 46.27 m

Volume = LxWxH

x (r3r2)2

= 8.17/46.27 = 0.17 m2

Let W = H

R32= (0.17/) + (5x10-2)2

R = 0.322 m


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CHAPTER 4: EXPERIMENTAL SETUP

4.1 INTRODUCTION

This chapter contains the description of our working experimental setup. On the basis of

theoretical analysis and calculation we have been developing a model which shows the

performance of our project and it helps to understand the working of ETAC. The basic

technology and principle of ETAC is based on heat transfer between air and soil which also

contain water.

4.2 MATERIAL SELECTION:-

The articles use everything from thin wall plastic sewer pipe up through large concrete

pipes. Metal tubes are also used. Lower conductivity of the plastic pipe is likely to affect

performance much given the fairly low conductivity of the inside air film and the relatively low

conductivity of the dirt. The main considerations in selecting tube material are cost, strength,

corrosion resistance, and durability. Tubes made of aluminum, plastic, and other materials have

been used. The choice of material has little influence on thermal performance. Metal tubes are

easier to install, and are more corrosion resistant. We are using Galvanized Iron in this project.

Galvanize mechanical properties

Mechanical Properties of Galvanized Steel:

Galvanized steel is a special type of steel that is zinc plated. Galvanization is primarily

carried out on the surface of a steel to make it more resistance to corrosion. All galvanized steel

has a distinguishing metallic-gray appearance. The surface is also a hundred times smoother than

uncoated steel. Because of its high durability, galvanized steel has a wide range of applications

from creating steel frames for construction to making automobile parts. For example, truck and

bus bodies are made of galvanized steel. It is also used to build up high-tension electronic

towers, highway signs, protective gears, and in the manufacturing of metal pails.

Physical Protection: Galvanized steel is basically a steel substrate that is coated with zinc. Since

Zinc has anodic properties against iron, this type of coating prevents the corrosion in the

substrate. Galvanization is a primitive chemical process that has been practiced for hundreds of

years. Steel is immersed in a molten zinc to produce a coating of zinc-iron alloy. This zinc-iron


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alloy forms a barrier between the steel and the environment. Zinc is a highly reactive metal in an

electrochemical process, and therefore it is easily oxidized to form a coating which protects the

steel. Moreover, in galvanized steel, zinc being an active metal, spontaneously reacts with

atmospheric oxygen and carbon dioxide to create zinc carbonate which also resists rust

formation.

Low Melting Point: Galvanized steel has better conductivity than uncoated steel and iron. This

property of galvanized steel reduces the electrical resistance on the contact area and prevents the

steel from overheating when exposed to sunlight or mechanical fiction. Also, Fe-Zn alloy melts

at a much lower temperature than zinc. Due to lower melting point, galvanized steel is a suitable

candidate for welding where galvanized steel can be closely united by heating and allowing the

metals to flow together. Galvanized steel has a higher ductility compared to iron, so the electrical

density is highly reduced when pressure is applied from electrode the steel sheets in various

metallurgical processes.

Adhesion: Usually, Galvanized steel sheets are painted before use. This is because paint is quite

adhesive to galvanized steel and a painted surface increases the corrosion resistance that

galvanized steel already has. Before painting, it is necessary to clean the surface thoroughly.

Galvanized steel has a phosphate layer underneath the zinc coating because of ferrous-zinc alloy.

Solder ability: Another important mechanical property of galvanized steel is solder ability. One

can galvanize the steel sheet without exfoliating the surface film. The film can then be removed

by a simple solvent.

References: Steel-N.com: Galvanized Steel Corrosion Resistance General Properties

Sperko Engineering Services, Inc.: Welding Galvanized Steel-Safely

Properties of Galvanized Steel:

Galvanized steel is produced by coating the steel in zinc. The properties of galvanized

steel are a unique combination that make it ideal for use in interior and exterior applications such

as car bodies, appliances, nuts and bolts, roofs, and rebar.

Corrosion Resistance: According to the American Galvanizers Association, galvanized steel

resists corrosion up to 100 times better than uncoated steel.

Surface Appearance: All galvanized steel has a matte-gray appearance. Zinc coating applied by

using electro galvanizing is smoother than galvanized steel made with batch or continuous

galvanizing and allows for a higher quality finish when painted.


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Formability: The zinc coating on galvanized steel is resistant to cracking and loss of adhesion

when the steel is formed into a product.

Durability: The zinc coating does not require special handling to protect it during transport or

use. It is extremely durable and resistant to scratches from abrasion.

Recyclable: Steel is by far the most recycled material in North America. Galvanized steel is as

recyclable as other types of steel.

4.3 FLOW DIAGRAM

The flow diagram describes the flow of air through various stages in ETAC.

4.4 EXPERIMENTAL SETUP

The experiment set consists of a detail of experimentation, apparatus and analysis of

result to be achieved on the basis of literature review, theoretical analysis and calculations.

Apparatus

1. Blower with volume flow rate 3.78 m3/sec2. MS Pipe of length 9.6m depends upon model.3. Trench box of size 1.14x1.14x.94 m3.4. Mud clay soil.

HOT AIR INLET

AIR PASSING THROUGH PIPE

COOLING OF AIR IN HEAT EXCHENGER

COOLED AIR PASSES TO THE ROOM


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5. Water sprinkler6. Thermometers

4.5 BLOWER SELECTION

Blowers are selected on the basis of their performance, their power consumption and

according to requirement where it has been used generally 2 types of blowers are used. Blowers

can achieve much higher pressures than fans, as high as 1.20 kg/cm2. They are also used to

produce negative pressures for industrial vacuum systems. The centrifugal blower and the

positive displacement blower are two main types of blowers, which are described below.

1. Centrifugal blower: Centrifugal blowers look more like centrifugal pumps than fans. The

impeller is typically gear-driven and rotates as fast as 15,000 rpm. In multi-stage blowers, air is

accelerated as it passes through each impeller. In single-stage blower, air does not take many

turns, and hence it is more efficient. Centrifugal blowers typically operate against pressures of

0.35 to 0.70 kg/cm2, but can achieve higher pressures. One characteristic is that airflow tends to

drop drastically as system pressure increases, which can be a disadvantage in material conveying

systems that depend on a steady air volume. Because of this, they are most often used in

applications that are not prone to clogging.

Centrifugal Blower

2. Positive-displacement blowers: Positive displacement blowers have rotors, which "trap" air

and push it through housing. These blowers provide a constant volume of air even if the system

pressure varies. They are especially suitable for applications prone to clogging, since they can

produce enough pressure (typically up to 1.25 kg/cm2) to blow clogged materials free. They turn


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much slower than centrifugal blowers (e.g. 3,600 rpm) and are often belt driven to facilitate

speed changes.

Positive displacement blower

4.6 DESIGN PROCEDURE:-

1. Determine the summer temperature. The summer soil temperature at a depth of 10 ft [3 m] is

roughly equal to the average monthly dry bulbair temperature of the site. For a rough estimate of

the cooling capacity ofan earth tube installation calculate the average ambient temperature for

the entire cooling season and use this value as an estimate for the ground temperature at the site.

2. Determine desired tube exiting air temperature. Decide on the desired outflow air temperature

from the earth tube. This will be the supply air temperature (which must be several degrees lower

than room air temperature) if the earth tube installation is handling the entire cooling load (not

common or recommended). If the earth tube is pre-cooling air for air-conditioning system a

higher exiting temperature would be acceptable. It is unlikely that exiting air temperature will be

lower than 4 degrees above the temperature of the soil surrounding the tube.

3. Determine the soil moisture characteristics. From on site testing and observation, establish

whether the soil surrounding the earth tube will normally be dry, average, or wet. Which is based

upon average soil moisture the cooling capacity in wet soil conditions would be approximately


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twice as high as for average soil; for dry soil approximately half as great. Soil conditions play an

important role in earth tube performance.

4. Estimate the cooling load for the earth tube installation. Estimate the design cooling load for

the building based upon building type and size. This load will be expressed in kW. For an air

tempering installation, the earth tube load will be some reasonable portion of the full cooling

load. For outdoor air tempering, simply neutralizing the outdoor air load is the objective.

5. Determine the length of earth tube required to estimate the required length of earth tube. The

intersection of the value (Steps 1 and 2) and the cooling load (Step 4) gives the required tube

length. For wet or dry soil conditions use the adjustments noted in Step 3.

4.7 WORKING OF MODEL:-

An Earth air tube system is a one way open-air system. Outdoor fresh air is drawn into

the tubes, cooled (in the summer) by the Earth, dehumidified, and delivered to the inside of the

house via the furnace fan. This system provides fresh conditioned air to every room in the house.

The tube material is high-density MS pipe formed into drainage this pipe has a corrugated

structure, which doubles the surface area of the pipe allowing for more Earth contact and more

efficient heat exchange. It is corrosion resistant, easy to handle, non-toxic and readily available.The optimum tube diameter is 4.6cm. The larger diameter tubes require a longer buried run for

optimum performance. The tube has a multiple slit cut into it along the seam.

Larger diameter tubes require greater spacing between the tubes. The reason for the

spacing is to minimize the chance the tubes will exchange heat with one another rather than with

the surrounding soil. For 4.6cm diameter tubes the trench will need to be 1m deep, 1m wide and

1m long. For larger diameter tubes the trench will increase in depth, width, and length.

The trench drainage can be a gravity drain to daylight or the trench can direct the drain

water to a sump pump. The danger of using a sump pump is that if there is ever a loss of power

for an extended period of time the tubes and trench drainage system could fill with water. As a

result the interior of the tubes could become plugged beyond repair with silt and sludge.

The tube trench has to be very carefully constructed to assure proper drainage of water

and air tube condensate. An experienced installer should only attempt this construction, as any


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mistakes can ruin the installation and possibly threaten the health of those living in the house.

There are several trench design details that need to be implemented: trench profile, drainage,

tube installation, materials used, as well as depth and dimension of the trench according to the

diameter of the tubes.

The trench drainage can be a gravity drain to daylight or the trench can direct the drain

water to a sump pump. The danger of using a sump pump is that if there is ever a loss of power

for an extended period of time the tubes and trench drainage system could fill with water. As a

result the interior of the tubes could become plugged beyond repair with silt and sludge.

Model Drawing and Geometry

The following data is calculated by theoretical analysis and thermal calculation. The

model dimensions are discussed in fig no.

Length of box 114cm 1.14m

Width of box 100cm 1.14m

Height of box 94cm .94m

Total length of pipe in box9.6 m

Diameter of pipe4.6cm - .046m


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4.8 MATERIAL SPECIFICATION

Sr. No. Name of the parts Material Quantity

1. 2 GI Pipe (3 ft) Steel 9

2. 2 GI Pipe (1 ft) Steel 4

3. GI Elbow (2 dia.) Steel 13

4. Union Steel 1

5. 2 Coupling Steel 1

6. GI Metal Sheet Steel 5

7. Blower 0.25 HP 1

8. Clay - 1.4 m3

9. Themometer (0-50 C) - 2

10. Sling Psychrometer - 1


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4.9 REQUIREMENT OF M/C TOOLS AND MEASURING EQUIPMENTS

Requirment of Machine Tools Lathe Machine Welding Machine Plumber Tools Drilling Machine

Requirement of Different Equipments Cutting Tools Teflon tape Hammer File

Measuring Instruments

Thermometer Sling Psychrometer


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Assembling of pipe


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Ducted pipe


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Straight run pipe test


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Experimental Model (Trench & Pipe)


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4.10 EXPERIMENTATION

Average temperature of air in pipe(Ti1+Ti2+Ti3+Ti4)/2

Average temperature of Earth - (TE1+TE2+TE3)/3

T1 = Inlet temperature of air

T2 = Outlet temperature of air

Total length of pipe - 44 m

Velocity of air at inlet =

Velocity of air at outlet = 6m/min

4.11 RESULTS TO BE ACHIEVED

Inlet temperature of air = 45oC

Out let temperature of air = 30oC

Saturation Effectiveness = 80%

COP = 1.5

Characteristic Curves:

1. Velocity of air v/s Temperature From the analysis of literature and calculations ifvelocity of air gradually increases outlet temperature of air from pipe also increasesbecause air is poor thermal transfer medium therefore it takes some time to cool into the

pipe. If we increase the velocity it doesnt have time loss there heat.

2. Length of tube v/s Temperature As the length of tube increases DBT decreases,because if we increase the length of tube air have more time to loss there heat to

surrounding and it cools easily.

3. Velocity of air v/s COPVelocity of air increases co-efficient of performance decreasesbecause air have less time to loss its heat therefore outlet temperature increases and co-

efficient of performance decreases.


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CHAPTER 5

PRACTICAL ANALYSIS & READINGS

5.1 READINGS:

Straight pipe test at normal condition:

Date22/3/2011

Time Inlet

Temp

Outlet

Temp

Soil

Temp

11 am 32.1 25.7 24.8

12 noon 32.7 25.9 25

1 pm 33.2 26.3 25.3

2 pm 33.9 26.7 25.6

3 pm 34.3 26.9 25.8

4 pm 33 26.1 25.2

During Straight run test with heater:

11.30 34.5 25.2 24

11.45 37 27.5 25

12 40 28.3 26.2

12.15 41.5 28.5 26.6


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5.2 AIR TEMPERATURE INSIDE ETAC AND SOIL TEMPERATURE:

TIME INLET TEMP OF

AIR (C)

OUTLET TEMP

OF AIR (C)

SURFACE TEMP

OF PIPE (C)

10 AM 29.3 24.1 22.7

11 AM 30.1 24.7 23.3

12 NOON 32 25 23.9

1 PM 32.7 25.3 24.2

2 PM 34.2 26.2 25.1

3 PM 34.5 26.5 25.3

4 PM 33.5 26 25.1

5.3 CALCULATIONS OF ETAC MODEL:

Di = 0.046 m

Do = 0.060 m

Ti = 40 + 273 = 313 k

To = 29.5+273 = 302.5 k

Ts = 27+273 = 300 k

kp = 18 W/mK

hw = 500 W/ m2k

u = 20 m/s

Tam =

307.5k

Properties of air at 307.5 k:

= 1.1364 kg/m3

= 16.645 x 10-6

KJ/kg-K

ka = 26.8 x 10^-3 W/mk


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Pr = 0.7055

Calculations:

Re = (u x Di)/

= (20 x 0.046)/16.645x10-6 = 55271.85

Nu = 0.023 x Re^.8 x Pr.3 = 128.9

Nu = (ha x Di)/ka

ha = (Nu x ka)/Di

= (128.9 x 26.8 x 10-3)/0.046 =75.098 W/m2 k

Fouling factor:

Fouling factor (Rfo) = 0.0001m2k/w

Fouling factor (Rfi) = 0.00035 m2

k/w

Overall heat transfer coefficient based on outside tube surface can be expressed as

Overall heat transfer coefficient (Uo)

Uo = 1/ [{(Do/Di)/hi} + {(Do/Di)xRfi} + {Do*ln (Do/Di)/2kpipe} + Rfo + 1/hw]

Uo = 1/{.0173+4.55x10-4 +4.37x10-4 +0.0001+ 2x10-3}

= 49.28 W/ m2k

Ao = 3.14x .06x 7.5

= 1.143 m2

Log mean temperature (Tlm)

T1 = 313-300 = 13 K

T2 = 303-300 = 3 K

Tlm = (13-3)/ ln (13/3)

= 6.82 K

Q = Uo x Ao x Tlm

= 49.28 x 1.143 x 6.82


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= 474.89 W

= .143 TR

5.4 EARTH SOIL MODEL OF ETAC:Cooling time = 24 hrs

Amount of heat transferred in 24 hrs (Q) = .135TR = .143x210x60x24 J

Q = 40.82x106

J

Convection co-efficient of water (hw) = 500 W/m2 k

We know that

Q = [ mw CpwT + mE CpET]

mw = 20% mE

40.82x106

= [ 0.2 x mE x 4200 + mE x 880] x [39.527]

ME = 3169.65 kg.

Density of soil (soil) = 2050 kg/m3

[reference no 10]

Volume of soil = mass/ density

= 3169/2050

= 1.54 m3

Length of pipe = 7.5 m

Volume = Lx x (r32

r22

)

x (r32r2

2) = 1.54/7.5 = 0.2053 m

2

Let W = H

r3 = 0.076 m = 7.6 cm

Coefficient of Performance:

COP = Refrigerating effect

Work done

Refrigerating effect = cooling load = 475 W

Work done = Power consumption by blower = 187 W

COP = 2.54


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CHAPTER 6

COSTING

6.1 INTORDUCTON

It is the determination of actual cost of article after adding different expensive incurring

in various departments. It may also be definite as a system which systematically. Record and the

expenditure included in the various departments.

To determine any the cost of manufacture product.

6.2 AIM OF COSTING

The important aim and object of costing are as follows:

1. To determine the cost of each article.2. To determine the cost of each article operation to keep central over head expenses.3. To supply information for costing of wastage.4. It helps in reducing the total cost of manufacture.


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6.3 PURCHASE MATERIAL AND LABOUR COST

Sr.

No.

Name of Parts and Materials Rate Quantity Total Rupees

1. GI Steel Trench (1.14x1.14x0.94) 3000 1 3000

2. GI Steel Ducted Pipe 5100 14 5100

3. GI Steel Elbow 85/piece 13 1105

4. GI Steel union 150 1 150

5. Blower 2500 1 2500

6. Thermometer 150/piece 2 300

7. Sling Psychrometer 150 1 150

8. Teflon Tape 15/piece 10 150

9. Labour Charges - - 2500

TOTAL 14955


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CHAPTER 7

CONCLUSIONS

6.1Future Scope:Earth tubes can be further modified in its performance by addition of the fins and

instrumentation which further catalyses the performance of the whole system. The reduction

in the length of pipe and increase in diameter can also be achieved through various

performance factors.

Earth tubes (earth tubing) are, in a word, low-tech, sustainable, low electric, zero-energy passive

geothermal solar heating and cooling systems. Its an environmental friendly product. It does not

require any refrigerant or harmful chemical, which causes the green house effect. It is an

eco-friendly, pollution free cooling system which can help us to reduce carbon emission.

This type of project is already being used in developed countries like America and

some European countries where it uses as cooling as well as heating system. This type of

project helps India for pollution free environment. By some more experimentation and

research we can improve its efficiency and we can get better performance.

6.2 CONCLUSION

In order to reduce energy consumption for air-conditioning and maintaining thermal

comfort in buildings in Tropical climate, passive and low-energy strategies such as ETAC must

be considered as suitable options. This research has established the climatic and soil parameters

required to predict the thermal performance of ETAC in choose tropical locations. Thermal

simulation of the ETAC system has been developed within TRNSYS simulation environment to

study the thermal behavior of ETAC system in key sample Tropical climatic condition. A case

study of location Jalgaon, a Composite climate and a Hot-Humid climate, have been used.

The results of thermal simulations show that there is clearly a significant benefit of using

the system to reduce ventilation air temperature in both locations. The greatest benefit is in the

Jalgaon climate where there is significant diurnal and annual range of temperature, which results

in high annual sensible energy gain for cooling. The results have revealed that ETAC system

reduces ventilation air temperature, ventilation cooling load and could improve the coefficient of


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performance of mechanical air-conditioning systems. Tropical climate is characterized by high

solar radiation which provide high energy yield from Solar PV systems, the fan energy input

required to run the ETAC system may be fully or partially met using solar PV systems.

A single pass earth-tube air cooler (ETAC) was installed to study its performance in cooling and

heating mode. ETAC is made of 10 m long GI pipe of 4.6 cm nominal diameter and 3 mm wall

thickness. ETAC is buried in a trench deep below soil. A 187W blower pumps ambient air

through it. Air velocity in the pipe is 11 m/s. ETAC was able to reduce the temperature of hot

ambient air by as much as 14C in March-April. The basic soil temperature in March-April was

25.6C. It was able to warm up the cold ambient air by a similar amount in the nights of January.

The basic soil temperature in January was 24.2C.

The coefficient of performance (COP) in cooling mode averaged to 2.5-3.5. Cooling tests

were of 6 hour continuous duration during the day. In heating mode it averaged to 3.3. Heating

tests were of 14 hour continuous duration through the night. Based on the results it can be stated

that ETAC holds considerable promise as a means to cool or heat ambient air for a variety of

applications such as the livestock buildings and greenhouses.


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REFERENCES

1. Sharan G. and Jadhav R. (2003). Soil temperature regime at Ahmadabad. Journal ofAgricultural Engineering.

2. Evaluation of models for the calculation of earth-to-air heat exchangers, Didier DeKerpel.

3. Energy performance of earth-air heat exchanger in a belgian office building, A. Janssens,M. Steeman, J. Desmedt, H. Hoes, M. De paepe.

4. Earth Air Tubes, by Larry Larson.5. Puri V.M. (1986). Feasibility and performance curves for intermittent earth-tube heat

exchangers. Trans ASAE, 29(2). March-April, pp.526-532.6. Goswamy D.Y. and Dhaliwal A.S. (1985). Heat transfer analysis in environmental

control using an underground air tunnel. Journal of Solar Energy Engineering, vol.107,

pp.141-145.

7. Sharan G.; Sahu R.K. and Jadhav R. (2001). Earth-tube heat exchanger based air-conditioning for tiger dwellings. Zoos' Print, 16:5, May (RNI 2:8).

8. Ground-coupled Heat Exchanger from Wikipedia.9. Refrigeration and Air conditioning, Chapter 17 (Pg no 482-495) R.S.Khurmi.10.Engineering Heat and Mass transfer, M.M.Rathore, Appendix (pg 11121123).11.Paper of Bibliographic Search on the Potential of Earth Tubes.

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