# Thermal Performance and Exergy Analysis for Conical Fins with Rift

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## Abstract

This experimental research study has been conducted to analyze the second law and thermal performance of conical fins with rift. There are studies in the literature examining the effect of traditional circular fins and conical fins on heat transfer. However, there are no studies in the literature examining the methods for increasing the thermal performance of conical fins. This experimental study was conducted for the purpose of making up this deficiency. Besides the examination of thermal performance of the conical fins with rift, exergy analysis has also been carried out. That is, the study has been made more comprehensive. In addition to riftless conical fins, the experiments were carried out by using the fins with a rift spacing of 1.5 and 3.5 mm so that the boundary layer separation mechanism can be accelerated according to riftless conical fins. Experimental results for eight different velocities of air flow (2–20 m/s) have been presented. In the present study, experimental research was conducted on conical fins with and without rift at different inclination angles (45\(^{\circ }\), 60\(^{\circ }\) and 80\(^{\circ }\)). Thus, the inclination angle at which the conical fin with rift is better than the riftless conical fin has been determined in terms of thermal performance and exergy analysis. It has been found that the conical fin with rift at 60\({^{\circ }}\) inclination angle is better in terms of both thermal performance and the second law of efficiency, when compared with the riftless conical fin. These results for \({r} =1.5\) mm at \(\alpha =\) 60\(^{\circ }\) encourage the use of conical fins with rift compared to traditional circular fins in literature.

## Keywords

Thermal Performance Exergy Rift Efficiency## List of symbols

- \({A}_{\text {s}}\)
Sum heat transfer surface area (\(\text {m}^{\text {2}})\)

- \({A}_{\text {0}}\)
Surface area of tube between two fins \((\text {m}^{\text {2}})\)

- \({A}_{\text {fin}}\)
Area of the conical fin on the tube \((\text {m}^{\text {2}})\)

- \({A}_{\text {p}}\)
Area of section vertical to the direction of flow between two fins \((\text {m}^{\text {2}})\)

- \({c}_{\text {p,c}}\)
Specific heat of air (J/kg \(^{\circ }\)C)

- \({c}_{\text {h}}\)
Specific heat of water (J/kg \(^{\circ }\)C)

*C*Capacity rate (W/\(^{\circ }\)C)

*D*Outer diameter of heating tube (m)

- \(\dot{{E}}_{\text {D}} \)
Exergy destruction (W)

- \({e}_{\text {D}}\)
Dimensionless exergy destruction

*H*Height of conical fin (m)

*L*Length of heating tube (m)

- \(\dot{{m}}_{\text {c}}\)
Mass flow of air (kg/s)

- \(\dot{{m}}_{\text {h}}\)
Mass flow of water (kg/s)

*n*Number of conical fins

- NTU
Number of transfer units

*p*Pitch between conical fins (m)

- \({P}_{\text {c,in}}\text { }\)
Inlet pressure of air into test section (Pa)

- \({P}_{\text {c,out}} \)
Exit pressure of air from test section (Pa)

- \(\dot{{Q}}\)
Actual heat transfer (W)

- \(\dot{{Q}}_{\text {air}}\)
Heat transfer of air (W)

- \(\dot{{Q}}_{\text {water}}\)
Heat transfer of water (W)

- \(\dot{{Q}}_{\text {max}}\)
Maximum possible heat transfer (W)

*Re*Reynolds number

- \({R}_{\text {c}} \)
Gas constant of air (J/kg K)

*r*Rift spacing (mm)

*s*Specific entropy (J/kg K)

- \(\dot{{S}}_{\text {generation}} \)
Entropy generation (W/K)

- \({T}_{\text {c,in}}\)
Inlet temperature of air into test section (K)

- \({T}_{\text {c,out}}\)
Exit temperature of air from test section (K)

- \({T}_{\text {h,in}}\)
Inlet temperature of water to test section (K)

- \({T}_{\text {h,out}}\)
Exit temperature of water from test section (K)

- \({T}_{\text {e}}\)
Environmental temperature (K)

*t*Conical fin thickness (m)

*U*Overall heat transfer coefficient (W/m\(^{\text {2}}\) \(^{\circ }\)C)

- \(V_{\text {max}}\)
Maximum velocity (velocity between two conical fins) (m/s)

## Greek symbols

- \(\nu \)
Kinematic viscosity (m\(^{\text {2}}\)/s)

- \(\psi \)
Availability

- \(\alpha \)
Conical fin inclination angle (\({^{\circ }})\)

- \(\varepsilon \)
Effectiveness

- \(\eta _{\text {fin}}\)
Conical fin efficiency

- \(\eta _{\text {II}}\)
Second law efficiency

- \({\rho }_{\text {c}}\)
Density of air (kg/m\(^{\text {3}})\)

## Subscripts

- air
Air side

- c
Cold fluid

- D
Destruction

- e
Environmental condition

- h
Hot fluid

- in
Inlet

- max
Maximum

- min
Minimum

- out
Exit

- s
Sum

- water
Water side

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## References

- 1.Dizaji, H.S.; Khalilarya, S.; Jafarmadar, S.; Hashemian, M.; Khezri, M.: A comprehensive second law analysis for tube-in-tube helically coiled heat exchangers. Exp. Therm. Fluid Sci.
**76**, 118–125 (2016)CrossRefGoogle Scholar - 2.Dizaji, H.S.; Jafarmadar, S.; Hashemian, M.: The effect of flow, thermodynamic and geometrical characteristics on exergy loss in shell and coiled tube heat exchangers. Energy
**91**, 678–684 (2015)CrossRefGoogle Scholar - 3.Durmuş, A.: Heat transfer and exergy loss in cut out conical turbulators. Energy Convers. Manag.
**45**, 785–796 (2004)CrossRefGoogle Scholar - 4.Mert, S.O.; Reis, A.: Experimental performance investigation of a shell and tube exchanger by exergy based sensitivity analysis. Heat Mass Transf.
**52**, 1117–1123 (2016)CrossRefGoogle Scholar - 5.You, Y.; Fan, A.; Liang, Y.; Jin, S.; Liu, W.; Dai, F.: Entropy generation analysis for laminar thermal augmentation with conical strip inserts in horizontal circular tubes. Int. J. Therm. Sci.
**88**, 201–214 (2015)CrossRefGoogle Scholar - 6.Moosavi, A.; Abbasalizadeh, M.; Dizaji, H.S.: Optimization of heat transfer and pressure drop characteristics via air bubble injection inside a shell and coiled tube heat exchanger. Exp. Therm. Fluid Sci.
**78**, 1–9 (2016)CrossRefGoogle Scholar - 7.Swain, A.; Das, M.K.: Convective heat transfer and pressure drop over elliptical and smooth tube. Heat Transf. Asian Res.
**45**, 462–481 (2016)CrossRefGoogle Scholar - 8.Rao, J.B.B.; Raju, V.R.: Numerical and heat transfer analysis of shell and tube heat exchanger with circular and elliptical tubes. Int. J. Mech. Mater. Eng.
**11**, 1–18 (2016)CrossRefGoogle Scholar - 9.He, Z.; Fang, X.; Zhang, Z.; Gao, X.: Numerical investigation on performance comparison of Non-Newtonian fluid flow in vertical heat exchangers combined helical baffle with elliptic and circular tubes. App. Therm. Eng.
**100**, 84–97 (2016)CrossRefGoogle Scholar - 10.Yang, J.-F.; Zeng, M.; Wang, Q.-W.: Numerical investigation on shell-side performances of combined parallel and serial two shell-pass shell- and -tube heat exchangers with continuous helical baffles. App. Energy
**139**, 163–174 (2015)CrossRefGoogle Scholar - 11.Yakar, G.; Karabacak, R.: Investigation of thermal performance of perforated finned heat exchangers. Exp. Heat Transf.
**28**, 354–365 (2015)CrossRefGoogle Scholar - 12.Pahani, D.: Evaluation of Nusselt number and effectiveness for a vertical shell-coiled tube heat exchanger with air bubble injection into shell side. Exp. Heat Transf.
**30**, 179–191 (2017)CrossRefGoogle Scholar - 13.Jia-dong, J.I.; Pei-qi, G.E.; Wen-bo, B.I.: Numerical investigation of flow and heat transfer performances of horizontal spiral-coil pipes. J. Hydrodyn.
**28**, 576–584 (2016)CrossRefGoogle Scholar - 14.Moffat, R.J.: Describing the uncertainties in experimental results. Exp. Therm. Fluid Sci.
**1**, 3–17 (1988)CrossRefGoogle Scholar - 15.Çengel, Y.A.: Heat and Mass Transfer: A Practical Approach, 3rd edn. McGraw-Hill, New York (2006)Google Scholar