Heat Transfer Enhancment using Wireloop Tube Inserts in an Oil Cooler

Heat Transfer Enhancment utilizing Wireloop Tube Inserts in an Oil Cooler

Abstraction

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By and large, Air blast Oil Coolers are used for chilling the bearing oil of Gas Turbines, Hydro-generators, Induced Draft & A ; Forced Draft fans for boilers etc. By and large the oil side flow is in the laminar zone at the operating conditions. Hence there is a demand for tube side turbulent boosters to accomplish higher heat transportation coefficient. Hence use of enhanced heat transportation techniques by infixing wire cringle inserts on the tube side can heighten the heat transportation coefficient by about 3-4 times and the size of the heat money changer can be reduced. These techniques can be applied to other applications like provender H2O warmers besides. Thorough literature study was carried out to understand the province of the art engineering. Subsequently, after analyzing the literature, conceptual design of wire cringle was carried out in such a manner that broad scope of experimental informations can be generated. A exemplary oil ice chest with H2O on shell side and oil on tubing side was designed along with the necessary instrumentality tapping sing design inside informations of typical oil ice chest. The instrumentality consists of measuring of flows, force per unit areas and differential force per unit areas, utilizing a province of the art informations logging system. All the instruments were calibrated before utilizing them. Excess measurings were provided for guaranting right readings even when some of the detectors fail during operation. Detailed experimental agenda was prepared. A process for operation and control of the trial set up was evolved and consequently the experiments are carried out on the theoretical account with and without tubing inserts. A computing machine plan was developed for the rating of trial informations. Using the plan all the trial information was analysed and consequences were tabulated and presented. It was found that the sweetening of tube side heat transportation coefficient with inserts is from 2 to 8 times that of field tubing heat transportation coefficient. It is besides found that the enhancement factor increased with the addition in Reynolds figure. However there is a considerable addition in tube side force per unit area bead compared to that of field tubing force per unit area bead. In this study, literature study, preparations, sample computations, description of trial set up with instrumentality, consequences and analysis, range for farther work, decisions, recommendations and list of mentions are presented.

Introduction

ENHANCED HEAT TRANSFER:

From Newton’s jurisprudence of chilling, the rate of heat transportation to or from a fluid fluxing in a tubing can be expressed as

Q = H*As*?Tave…………… . ( 1 )

Where ‘h’ is the mean heat transportation coefficient

‘As’is the heat transportation surface country ( it is equal to ?DL for a round pipe of length L and diameter D )

‘?Tave’ is some appropriate mean temperature difference between the fluid and the surface.

From equation ( 1 ) , ‘Q’ can be increased by increasing ‘h’ or by increasing ‘As

Hence enhanced heat transportation can be achieved by two methods. They are by I ) Enhanced surfaces and by two ) Enhanced heat transportation coefficient.

Enhanced surfaces:

By increasing the heat transportation country, rate of heat transportation can be increased. When one of the fluids involved in heat transportation in a heat money changer is of low heat transportation coefficient like air, so surface country on that side is enhanced in signifier of drawn-out surfaces calledfives. Finned tubings used in air cooled heat money changers are good illustrations for enhanced surfaces.

Enhancement of heat transportation coefficient:

Tube side heat transportation coefficient can be enhanced by internal augmentation utilizing devices called tubing inserts, which are discussed below in item.

Tube inserts

Thermal boundary bed consequence is more in laminar flow than disruptive flow. Hence turbulency is to be promoted in laminar flow. For this purpose devices calledtubing insertsare provided on tube side as turbulency boosters. In the present work Wire cringle inserts have been designed and manufactured for survey of sweetening in tube side heat transportation coefficient compared to kick tube values.

Type’s tubing inserts:

Different types of tubing inserts used boulder clay day of the month are:

A ) Twisted tape inserts,

B ) Helical coiled inserts,

C ) Core rods and

fallingfilmdistributionD ) Wire matrix elements.

Shell Side Fluid: Water

Pictures demoing tubing inserts and turbulency promoted by inserts in fluid flow

Tube Side Fluid: Oil ( ISO-VG-32 class )

By and large ISO-VG-32 class oil is used as bearing oil for gas turbines, induced bill of exchange and forced bill of exchange fans. So the same oil is used in the present experiment. The belongingss like denseness, viscousness, specific heat and thermic conduction of the oil alteration with temperature. As such they are called as thermo physical belongingss. The providers have provided these belongingss. These belongingss play a important function in the constitution of informations from the experiments.

Thermo physical belongingss of oil (ISO-VG-32 class )

SNO:

Temperature

Density

Dynamic viscousness

Specific heat

Thermal

conduction

OC

Kg/m3

Kg/m-s

KJ/KgOC

W/mOC

1

40

855.5

0.0272

2.134

0.1327

2

50

849.5

0.01869

2.179

0.1319

3

60

843.5

0.01269

2.242

0.1312

4

70

837.5

0.00963

2.27

0.1305

5

80

831.5

0.00715

2.31

0.1302

6

90

825.5

0.005572

2.38

0.1290

Experimental process:

The inside informations of experimental agenda are as shown in the Table No 1. Experiments were conducted with and with out wire cringle inserts at different oil flow rates keeping the oil recess temperature as 55OC, 70OC & A ; 85OC.

The assorted parametric quantities monitored and recorded are as follows

  • Oil flow rate
  • Water flow rate
  • Water recess temperature
  • Water mercantile establishment temperature
  • Oil recess temperature
  • Oil mercantile establishment temperature
  • Oil recess force per unit area
  • Water recess force per unit area
  • Differential force per unit area across heat money changer
  • Tube wall temperatures at different locations
  • Oil armored combat vehicle temperature

The above obtained values are substituted in the expression available both theoretical and Experimental values for computation of rate of heat transportation ( Q ) , heat transportation coefficient ( H ) , non dimensional Numberss ( RE, Pr, Nu ) , Pressure drops ( displaced person ) and clash factors ( degree Fahrenheit ) .

All the above values obtained are tabulated and Graphs are plotted as annexed.

OBSERVATIONS & A ; CONCLUSIONS

1. The mistake between heat transportation coefficients calculated from field tubing experiments and from Sider & A ; Tate correlativity is 1-25 % . This is due divergence of oil belongingss from the expected belongingss due to debasement of oil by frequent warming and due to mistakes in measurings of temperatures and flow rates even after standardization.

2.In insert tubings compared to kick tubes tube side heat transportation coefficient and Nusselt Numberss have enhanced by

I ) 2-5 times with Reynolds Numberss from 200-1000 from the experiment with oil recess temperature around 55OC.

two ) 2-6 times with Reynolds Numberss from 200-1700 from the experiment with oil recess temperature around 70OC.

three ) 1.7-5.5 times with Reynolds Numberss from 200-2100 from the experiment with oil recess temperature around 85OC.

All these observations suggest that temperature consequence on heat transportation coefficient is non much as the enhancement ratios in the three instances are indistinguishable.

3. Pressure drops in insert tubings compared to kick tubes has increased by

I ) 4.5-14.5 times with Reynolds Numberss from 200-1000 from the experiment with oil recess temperature around 55OC.

two ) 8-14 times with Reynolds Numberss from 200-1700 from the experiment with oil recess temperature around 70OC.

three ) 9-14.7 times with Reynolds Numberss from 200-2100 from the experiment with oil recess temperature around 85OC.

Further it is observed that for same Reynolds figure, the force per unit area bead somewhat increases with lessening in oil temperature. This is because of addition in viscousness and denseness of oil with lessening in oil temperature.

4. Friction factor in insert tubings compared to kick tubings has gone up by 9-10 times for all the three sets of experiments.

5. Overall heat transportation coefficients have enhanced by 2- 5 times in insert tubings compared to kick tubings for all the three sets experiments.

Recommendation

  1. More experiments should be done by changing some more parametric quantities of inserts like cringle denseness, angle of Curvature of the inserts and cringle wire diameter.
  2. Inserts of cringle densenesss 400,500,600 loops/meter are to be developed and tested. Lower cringle denseness inserts lesser than the 300 loops/meter are to be tested to convey down the force per unit area bead, which is enormous in the present instance.
  3. Using the consequences obtained from experiments with several discrepancies of inserts can be analysed for Nusselt figure, heat transportation coefficient, frictional force per unit area bead, clash factor and enhancement ratio of heat transportation coefficient and suited generalized correlativities can be developed for different geometric fluctuations.
  4. Cost analysis and feasibleness survey taking into history the addition in pumping capacity of enhanced heat money changers utilizing the wire cringle inserts has to be carried out.
  5. Prototype heat money changer development with inserts for any typical applications can be initiated.

Mentions

Documents:

1. Arthur A.E. Bergles. “Enhancement of heat transfer” .

2 G.T.Polley “Applications of Heat Transfer ehancement” , 2001. www.pinchtechnology.com.

3. S.B.Uttarwar and M. Raja Rao, 1985, “Augmentation of Laminar Flow Heat Transfer in

Tubes by agencies of wire spiral inserts”ASME JOURNAL OF HEAT TRANSFER, vol.107,

Pp.930-935.

4. V.D. Zimparov and P.J. Penchev, 2004, “Performance Evaluation of Some Tube inserts as

Heat transportation sweetening techniques” , 3rd International Conference on Heat Transfer,

Fluid Mechanics and Thermodynamics, Cape Town, South Africa.

5. Webb R.L. , 1994 “Principles of Enhanced Heat Transfer” , John Wiley and Sons, New York.

6. Bergles A.E. , 1997, “Heat Transfer Enhancement-the encouragement and adjustment of high heat fluxes” , ASME, diary of Heat Transfer, 119, 8-19.

7. Kalinin E.K. , Dreitser G.A. , Kopp I.Z. and Mykochin A.S. , 2002, “Efficient Surfaces for Heat Exchangers. Fundamentalss and Design” , Begell House Inc. , New York, Wallingford ( UK ) .

8. Bejan.A. , 1982 “Entropy Generation through Heat and Fluid Flow” , John Wiley and Sons, New York.

9. Bejan.A, 1996, “Entropy Generation Minimization” , CRC Press, Boca Raton, FL

Books:

10.Tema Standards.

11.Process Heat Transfer – Donald Q.Kern

12.Heat Transportation By J.P. Holman

13.Heat Transfer – A Practical Approach By Yunus A. Cengel

14.Heat Transfer- A Basic Approach By M.N.Ozisik.

15.Heat Transfer- Principles And Applications By Binay K.Dutta

16.Heat Transportation By R.C.Sachdeva

Table of experiments

Exp.

Type

Oil recess temp (OC )

Oil flow rate, m3/ hour

0.2

0.3

0.5

0.7

0.9

1.0

1.1

1.2

1.3

1.4

1.5

1.6

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

7.5

Plain tubing

55

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

75

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

85

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

Insert Tube 300Loop/meter

55

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

75

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

85

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

* Flow rates are declarative merely.

*No. of experiments are probationary merely.

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