Browsing by Author "Janjua, Muhammad Mansoor"

Now showing 1 - 4 of 4

A critical review on heat transfer augmentation of phase change materials embedded with porous materials/foams
(2019-06-01)
Tauseef-ur-Rehman
;
Ali, Hafiz Muhammad
;
Janjua, Muhammad Mansoor
;
Sajjad, Uzair
;
Yan, Wei-Mon
Phase change material (PCM) is promising media for thermal energy storage owing to its extensive value of latent heat (140-970 KJ/Kg). However, thermal conductivity of PCMs is too low which obstructs energy storage and retrieval rate. In recent days, thermally enhanced PCMs are considered promising materials for efficient heat transfer in many applications. This article designates the review on improved thermal properties and heat transfer of PCMs by using porous materials. Enhanced heat transfer of PCMs can be achieved using extended surfaces (triangular, conical, square, and rectangular fins), heat pipes, and addition of highly conductive nanoparticles (e.g. Cu, Al2O3, Au, SiC, SiO2 and TiO2). Major focus of this article is to study the enhanced heat transfer of PCMs through metallic (copper, nickel, and aluminum) and carbon based (carbon, graphite and expanded graphite) porous materials/foams. Effects of porosity and pore density on heat transfer, thermal conductivity, specific heat, latent heat and charging/discharging time are critically reviewed. Porous materials/foams are reported to be efficient for heat transfer/thermal conductivity enhancement by 3-500 times. Furthermore, correlations to find the effective thermal conductivity of PCM/foam are reported. Important applications of PCM/foam reported by different researchers are also discussed in this paper. Finally, conclusions and recommendations are presented to highlight the research gap in this area. (C) 2019 Elsevier Ltd. All rights reserved.
Condensing heat transfer coefficients of R134a in smooth and grooved multiport flat tubes of automotive heat exchanger: An experimental investigation
(2019-05-01)
Ammar, Syed Muhammad
;
Abbas, Naseem
;
Abbas, Saleem
;
Ali, Hafiz Muhammad
;
Hussain, Iftikhar
Condensation heat transfer coefficient of R134a was obtained in multi-port micro channel smooth and grooved flat tubes of automotive heat exchanger. The test consisted of two smooth and one grooved tube. The test range covered mass flux 490-1600 kg/m(2) s, heat flux 5.5-19 kW/m(2) and saturation temperature 51-68 degrees C. Results revealed that condensation heat transfer coefficient increased with an increment of mass flux, vapor quality and decreased with the increase of saturation temperature. The effect of heat flux on heat transfer coefficient was negligible. The grooved tube showed larger heat transfer coefficient than that of smooth tubes. A comparison of the present data of flat tube with existing correlations revealed that the heat transfer coefficient was not reasonably predicted, therefore new correlation was developed for heat transfer coefficient that predicted 86% data within +/- 30% with a mean error of 16%. (C) 2019 Elsevier Ltd. All rights reserved.
Nanofluid: Potential evaluation in automotive radiator
(2020-01-01)
Abbas, Farrukh
;
Ali, Hafiz Muhammad
;
Shah, Tayyab Raza
;
Babar, Hamza
;
Janjua, Muhammad Mansoor
Characteristic potential of nanofluids compared to conventional fluids (i.e. water, ethylene glycol, and oils) reported by numerous researchers has extended the concept of their use in multifarious systems. Idiosyncratic thermal and hydrodynamic behavior of nanofluids makes them best candidate to be used in automotive thermal management This article provides comprehensive review of applied research conducted on the potential evaluation of nanofluids in automotive cooling systems. All the key parameters that chiefly influence the nanofluid's performance in a cooling system have been identified along with logical discussion in the current study. Nanofluid assisted thermal management of automotive has been proved to be lucrative, however, ephemeral sustainability of nanofluids poses the major challenge. Set back of thermally effective nanofluids is their trivial suspension period. To alleviate the complication of sustainability of high thermal conductive nanofluids, scientists developed a new class of nanofluids called hybrid nanofluids. Hybrid nanofluids contain two kinds of nanopartides - one having high thermal conductivity and the other having high sustainability - resulting in a comparatively stable and thermally effective nanofluid. Hybrid nanofluids have merely been tested in an automotive cooling system. This study has also discussed the potential of hybrid nanofluids if employed for automotive thermal management. (C) 2019 Elsevier B.V. All rights reserved.
Thermal performance of LHSU for electronics under steady and transient operations modes
(2018-12-01)
Ali, Hafiz Muhammad
;
Arshad, Adeel
;
Janjua, Muhammad Mansoor
;
Baig, Wajahat
;
Sajjad, Uzair
This experimental study investigates the effect of passive cooling of electronic devices using a latent heat storage unit (LHSU) filled with n-eicosane as phase change material (PCM),under steady-state and transient heating operations. A pin-fin heat sink of square configuration, made of aluminum, pin fins acted as a thermal conductivity enhancers (TCEs), is used to augment the rate of heat transfer through n-eicosane which has low thermal conductivity. A range of input heating loads from 1.2-2.8 kW/m(2) with an interval of 0.4 kW/m(2) are applied at the base of LHSU, filled at three different volumetric fractions of n-eicosane, to quantify the steady-state and transient heat transfer characteristics for different operation modes for reliable passive cooling of electronics. The results are reported under two phases i.e. steady-state and transient heating, and thermal performance of LHSU is elucidated in terms of enhancement in operation time, enhancement ratio, effect of PCM amount and various usage modes under different heating loads. (C) 2018 Elsevier Ltd. All rights reserved.