Dr.Manoj Kumar.P et al, International Journal of Technology and Engineering Science [IJTES]TM Volume 4 [2], pp: 8013-8017, September 2016

ISSN: 2320-8007 8013

Design of a Heat Exchanger for a Compact

Natural Gas Compressor Dr. P. Manoj Kumar1 Dr.S.L.V.Prasad2 Ananda Mohan Vemula3

M. Prakash Babu4 R.Bhushana Rao5

1Department of Mechanical Engineering, Professor, Guru Nanak Institutions Technical Campus, Hyderabad, Telangana

State, (India)

2Department of Mechanical Engineering, Professor, Sri Venkateswara Institute of Technology, Anantapur, Andhra Pradesh

(India)

3, 4,5Department of Mechanical Engineering, Associate Professor, Guru Nanak Institutions Technical Campus, Hyderabad,

Telangana State, (India)

Abstract: Natural gas is an important fossil fuel. In order

to optimize the transportation of natural gas from the

source to the consumers, it must first be compressed. As

natural gas is compressed, the temperature increases

significantly and must be cooled before it can be

processed further. However, current heat exchangers for

this application are large and inefficient for a natural gas

compression skid. The devices must operate in locations

where there is a limited amount of space, such as

offshore oil platforms, it is crucial to reduce the footprint

as much as possible. The objective of this paper is to

design a more efficient and compact heat exchanger is

used in conjunction with rotary, positive-displacement

natural gas compressor. The design incorporated heat

pipes as a means to improve the efficiency of the overall

heat transfer.

Keyword: Compressor, Heat Exchanger, Heat pipe, Natural

Gas

1. INTRODUCTION

Natural gas is found in oil or gas wells and consists

primarily of methane (85% to 95% by volume) in

addition to trace amounts of other gases [1]. Natural

gas is used in many applications such as power

generation and running industrial equipment.

Compression of this gas is necessary to maximize the

amount that can be stored and transported.

Traditional natural gas compression systems require

multiple compression and cooling stages to achieve

high pressure ratios and reduce the temperature

increases caused by compression, respectively [2].

Since the gas is at different pressures after each

stage, multiple pieces of equipments are required

which greatly increases the amount of space the

equipment occupies. If the natural gas could be

compressed in fewer cycles, the size of the

compression platform could be greatly reduced. This

is particularly important on oil rigs and other

locations where space is limited [3]. Their

compressor uses dynamic liquid injection to achieve

near-isothermal compression. Since the gas is cooled

within the compressor, the entire compression can be

done in one cycle, and this allows the compressor to

be packaged on a smaller frame [4]. Currently, the

largest component on the compressor platform is the

cooler. The compressor skid holds the compressor

and all other components required to keep it running.

The cooler is used to cool the engine fluids, from the

engine running the compressor, the natural gas

coolant, and the natural gas itself. Current industry

standard coolers are approximately 7X3 Meters

[84m3

in volume] and have a flow rate of 378

SCFM. If the cooler could be redesigned as a more

efficient component, the size could be reduced,

allowing for a smaller compression skid [5]. This is

important because transporting the heavy, bulky

skids is expensive and difficult. This becomes even

more important in off-shore and under-sea

Dr.Manoj Kumar.P et al, International Journal of Technology and Engineering Science [IJTES]TM Volume 4 [2], pp: 8013-8017, September 2016

ISSN: 2320-8007 8014

application where optimizing of the footprint is of

most importance.

The goal of this project is to design a cooler that is

more efficient and compact than industry standard to

be used in conjunction with rotary, positive-

displacement natural gas compressor. The objective

of our project is to design a working cooler section

and to build a test model. This test model will be a

scale version of the full unit [6].

2. DESIGN METHODOLOGY

CATIA enables the creation of 3D parts, from 3D

sketches, sheet metal, composites, and molded, forged

or tooling parts up to the definition of mechanical

assemblies. The software provides advanced

technologies for mechanical surfacing. It provides

tools to complete product definition, including

functional tolerances as well as kinematics definition.

CATIA provides a wide range of applications for

tooling design, for

both generic tooling and mould and die [7].

3.DESIGN PROCESS

3.1 HEAT PIPE SPECIFICATIONS:

Length: 120 mm

Diameter: 8 mm

Thickness: 1.3 mm

Material:pure copper

Thremal conductivity(k):386.0𝑤

𝑚.𝑘

Specific heat (C):383𝐽

𝑘𝑔.𝑘

Fig:3.1 Heat pipe(Copper) design

Fig :3.2. Heat pipe with more number of fins

3.2 Two FIN SPECIFICATIONS:

Length : 75 mm

Width : 45 mm

Thickness : 8 mm

Fin Material : Pure Aluminium

Thremal conductivity(k):204.2𝑤

𝑚.𝑘

Fig 3.2.1: Cradle design (copper)

Fig 3.2.2:Design of fins

Dr.Manoj Kumar.P et al, International Journal of Technology and Engineering Science [IJTES]TM Volume 4 [2], pp: 8013-8017, September 2016

ISSN: 2320-8007 8015

3.3 NATURAL GAS PIPE SPECIFICATION

Length: 130 mm

Outer Diameter: 16 mm

Inner Diameter: 13 mm

Material: Alluminium alloy 2024

Thremal conductivity(k) : 177.0.𝑤

𝑚.𝑘

Specific Heat (C ) : 875 𝐽

𝑘𝑔.𝑘

3.4 FINAL DESIGN

Fig:3.4.1 Aluminium pipe design

Fig: 3.4.2 Sectional view of final design

Fig: 3.4.3 Cross sectional view of final design

Fig 3.4.4 General layout of the full length design

4. RESULTS AND DISCUSSTION

TABLE 4.1

EXPERIMENTATION ON BIKE

Fig: 4.1 Temperature vs. Length of Gas Pipe line

(Bike)

Temp Change ᵒC Length of Gas Pipe

Line(cm)

70 10

69 20

68 30

70 50

55 60

45 70

0

10

20

30

40

50

60

70

80

0 50 100

T

e

m

p

.

C

h

a

n

g

e

Length of Gas Pipe Line (cm)

WITHCRADLES

WITHOUTCRADLES

Dr.Manoj Kumar.P et al, International Journal of Technology and Engineering Science [IJTES]TM Volume 4 [2], pp: 8013-8017, September 2016

ISSN: 2320-8007 8016

Fig-4.1 shows a significant downfall of temperature

when cradles are placed along the gas pipe line, it has

been a decrease of temperature from 700C to 440C and

is arranged at the second half of the gas pipe so that

there could be a comparison of temperature change.

When there is no cradles placed temperature there is

negligible decrease in temperature with 1 and 2

degrees which is very minute [8].

TABLE: 4. 2

Experimentation on car

Temp

Change ᵒC

Length of Gas Pipe

Line(cm)

125 10

123 20

122 35

123 50

95 65

75 75

Fig: 4.2 Temperature Vs Length of gas pipe line

(Car)

From the Fig: 4.2, reading were taken from a car

exhaust. X-axis coordinates and gas pipe length

measurement on Y- axis the temperature change can

also be observed the same thing again it has been a

rapid fall down of temperature from 1230C to 650C

can be noticed this is a good result with arrangement

of cradles [9].

Table: 4.3

With Heat Pipe without Heat Pipe (Bike)

Fig: 4.3 With Heat Pipe Without Heat Pipe(Bike)

From the above Fig:3 it has been observed that use of

heat pipes were brought down to the temperature of

exhaust from 700C to 460C and this was arranged after

half the way from the beginning of the gas pipe. Heat

pipe has been filled with water and tested so that much

temperature has been brought down

Table: 4.4

With Heat Pipe without Heat Pipe (Car)

Temp Change0 C Length of Gas Pipe Line(cm)

70 10

66 25

61 40

62 55

49 70

40 85

Temp.

Change0C Length of Gas Pipe Line (cm)

120 10

114 20

110 35

110 50

95 65

70 75

0

20

40

60

80

100

120

140

0 50 100

T

E

M

P

C

H

A

N

G

E

ᵒ

C

Length of Gas Line (cm)

WITH CRADLES

WITHOUT CRADLES

0

20

40

60

80

0 50 100

T

E

M

P

C

H

A

N

G

E

ᵒ

C

Lenth of Gas Pipe (cm)

WITH HEAT PIPE

WITHOUT HEAT PIPE

Dr.Manoj Kumar.P et al, International Journal of Technology and Engineering Science [IJTES]TM Volume 4 [2], pp: 8013-8017, September 2016

ISSN: 2320-8007 8017

0

20

40

60

80

100

120

140

0 50 100

T

E

M

P

C

H

A

N

G

E

ᵒ

C

Length of Gas Pipe (cm)

WITH HEAT PIPE

WITHOUT HEAT PIPES

Fig: 4.4 With Heat Pipe without Heat Pipe (Car)

From the Fig:4.4 showed that the use of heat pipes

have been brought down the temperature of exhaust

from 1200Cto 640C d and this was arranged after half

the way from the beginning of the gas pipe heat pipe

has been filled with water and has been tested so that

the temperature was brought down.

TABLE: 5.5

With Fins & Without Fins (Car)

Temp Change0C (Car) Length of Gas Pipe

Line(cm)

125 10

117 25

108 40

106 50

87 66

66 80

Fig: 5 With Fins & Without Fin (Car)

The above Fig: 5 showed that taking gas pipe line on

X-axis and temperature change on Y- axis, after the

arrangement of fins it has been recorded a much

temperature brought down around 450C and use of

aluminum fins made this very easy, fins have been

after half the way from the start of gas pipe, all the

temperatures are recorded using a thermocouple and

experimented.

5. CONCLUSIONS

From the analysis to conclude that the model has a

significantly smaller footprint (21.5%) compared to

the current cooler in the market. This proves that the

design is a viable solution for natural gas compressors.

The experiment made to know that decreasing the foot

print made a significant increase in the heat efficiency

of the set up and got an efficiency of 74%. The

number of heat pipes increase, the cooler performance

also increases, the number of cradles and heat pipes

allowed for more heat is removed from the exhaust.

References

[1] A. Benjan.”Counter flow of heat exchanger

with core and plenuas at both ends.” critical inquiry 11

[2] Cengel-Mcgraw hills. Heat and mass transfer

[3] C P. Kothandaran. Heat and mass transfer data

book

[4] D Q Kern and AD Kraus. Extended surface

heat transfer

[5] Enerton. ”Designing with heat pipes.”2011

[6] R.K.Rajput. Heat and mass transfer

[7] Shah R.K. Fundamentals of heat exchangers:

Chapter 1

[8] S.kokac. Heat exchangers-Thermal hydraulic

fundamentals and design

[9] W.M.Kays and A.C.London. Compact heat

exchangers

Dr P.Manoj Kumar M.E;Ph.D, 16

years teaching experience, Published

12 publications. Area of Research is

IC Engines Nominated for Doctoral

committee member for Ph.D students

in VIT University.

0

20

40

60

80

100

120

140

0 50 100

T

E

M

P

C

H

A

N

G

E

ᵒ

C

Lenghth of Gas Pipe(cm)

WITH FINS

WITHOUT FINS