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As **the** number **of** transistors increases with new generation **of** microprocessor chips, **the** power draw and **heat** load to dissipate during operation increases. As a result **of** increasing **the** **heat** loads and **heat** fluxes **the** Conventional cooling technologies such as fan, **heat** sinks are unable to absorb and **heat** **transfer** excess **heat** dissipated by these new microprocessor. So, new technologies are needed to improve **the** **heat** removal capacity. In **the** present work single phase liquid cooling system with mini channel is analyzed and experimentally investigated. Mini channels are chosen as to provide higher **heat** **transfer** co-efficient than conventional channel. Copper pipes **of** 0.36 mm diameter are taken to fabricate **heat** sink and **heat** exchanger. A pump is used to circulate **the** fluid through **heat** sink and **heat** exchanger. A solid heated aluminium block to simulate **heat** generated electronic component is used and electrical input is supplied to **the** heated aluminium block and cooling system is placed **over** **the** heated block. **The** performance **of** **the** cooling system is analyzed from **the** **experimental** data obtained. It is experimentally observed that **the** mini channel liquid cooling system with water as a coolant has better performance than diluted ethylene glycol as coolant at different flow rates. **The** **surface** temperature **of** **the** heated aluminium block with convective **heat** **transfer** co-efficient is observed

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A comprehensive theoretical and **experimental** study was carried out on **the** thermal performance **of** a pin fin **heat** sink. An **experimental** model was shows that have **the** capability **of** predicting influence **of** effective **surface** area **of** pin fin on thermal **heat** **transfer** coefficient. Pin fin array are used in many applications to enhance **heat** **transfer** and also shows **enhancement** **of** **heat** **transfer** coefficient for different material **of** fin. Several different type **of** experiment test were run out with corresponding variation including **the** material **of** pin fin and different perforation on pin fin .Perforation with circular cross section are along **the** height **of** pin fin and there number varies from 1 to 3. **The** result indicates that **the** material having higher thermal conductivity with higher number **of** perforation gives more **heat** **transfer** coefficient. **The** effect **of** perforation on **heat** **transfer** was investigated.

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Fu and Yang (2001a) observed **the** **heat** **transfer** phenomena induced by moving square object. **The** finite element method with Arbitrary Lagrangian-Eulerian (ALE) method was used to simulate **the** moving boundary problem. **The** results indicated that **the** **heat** **transfer** rate remarkably increased when object moved in opposition to flowing fluid. Fu and Yang (2001b) presented **the** new concept **of** cooling strategy, **the** swing fins. **The** study was conducted by finite element method with ALE. It could be seen that swing fins clearly disrupted **the** thermal and velocity boundary layers along **the** fin **surface**. **Heat** **transfer** would be improving when fins moved at large speed. However, when fins were swinging at low speed, **the** results were similar to **the** flow **over** flat plate without vibration. Fu et al. (2001) numerically investigated **heat** **transfer** rate from **heat** plate with jet impingement. **The** **heat** **transfer** performance was improved by implementing **the** moving block on **the** plate **surface**. After installing moving block, thermal boundary layer was eliminated and new thermal boundary layer was formed. These phenomena clearly improved **the** **heat** **transfer** performance. **The** results indicated that increment **of** **heat** **transfer** rate was approximately 200% at **the** highest Reynolds number. Fu and Tong (2002) used finite element method with ALE to study **heat** **transfer** characteristic from heated

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Bayram Sahin, Alparslan Demir [2] studied **the** **heat** **transfer** **enhancement** and **the** corresponding pressure drop **over** a flat **surface** equipped with square cross-sectional perforated pin fins in a rectangular channel. **The** experiments covered **the** following range: Reynolds number 13,500 –42,000, **the** clearance ratio (C/H) 0, 0.33 and 1, **the** inter-fin spacing ratio (Sy/D) 1.208, 1.524, 1.944 and 3.417. Correlation equations were developed for **the** **heat** **transfer**, friction factor and **enhancement** efficiency. **The** **experimental** results showed that **the** use **of** **the** square pin fins may lead to **heat** **transfer** **enhancement**. Both lower clearance ratio and lower inter-fin spacing ratio and comparatively lower Reynolds numbers are suggested for higher thermal performance.

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Teerapat Chompookham, Chinaruk Thianpong, Sutapat Kwankaomeng, Pongjet Promvonge[15] have done **Experimental** investigations to study **the** effect **of** combined wedge ribs and winglet type vortex generators (WVGs) on **heat** **transfer** and friction loss behaviors for turbulent airflow through a constant **heat** flux channel. To create a reverse flow in **the** channel, two types **of** wedge (right-triangle) ribs were introduced. Wedge ribs were pointing downstream and pointing upstream. **The** arrangements **of** both rib types placed inside **the** opposite channel walls are in-line and staggered arrays. To generate longitudinal vortex flows through **the** tested section, two pairs **of** **the** WVGs with **the** attack angle **of** 60° were mounted on **the** test channel entrance. **The** test channel had an aspect ratio, AR=10 and height, H=30 mm with a rib height, e/H=0.2 and rib pitch, P/H=1.33. **The** flow rate in terms **of** Reynolds numbers is based on **the** inlet hydraulic diameter **of** **the** channel ranging from 5000 to 22,000. **The** presence **of** **the** combined ribs and **the** WVGs shown **the** significant increase in **heat** **transfer** rate and friction loss **over** **the** smooth channel. **The** Nusselt number and friction factor values obtained from combined **the** ribs and **the** WVGs were found to be much higher than those from **the** ribs/WVGs alone. In conjunction with **the** WVGs, **the** in-line wedge pointing downstream provides **the** highest

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In **the** next sections, flow and **heat** **transfer** inside **the** boundary layers **of** a gravity-driven liquid film along a vertical preamble plate subject to nonuniform suction flow are modeled and analyzed. **The** **surface** suction velocity is considered to have power-law profile distri- bution. Both momentum and energy equations **of** **the** developing liquid film are transformed into nonsimilar equations and solved numerically. **The** skin friction coefficient, Nusselt number, and different **heat** **transfer** **enhancement** indicators are computed. **The** numerical solutions are validated with **the** asymptotic analytical ones. An extensive parametric study has been con- ducted in order to explore **the** influence **of** average sur- face suction velocity, suction velocity profile, Froude number, and Galilei number on **the** skin friction coeffi- cient, Nusselt number, and different **heat** **transfer** **enhancement** indicators.

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Now a days, **the** energy efficiency is an extremely important topic in view **of** thermal conductivity **enhancement** amongst **the** researchers. For this purpose **the** researchers considered **the** involvement **of** nanoparticles in **the** base fluid. Originally Masuda et al. (1996) reported **the** liquid dispersions **of** submicron particles or nanoparticles. After that, first time nanofluid term is used by Choi (1995). In comparison to **the** base fluids, thermal conductivity **of** nanofluid is too high that's why these have been used in many energetic systems such as cooling **of** nuclear systems, radiators, natural convection in enclosures etc. **The** model proposed by Buongiorno (2006) studies **the** Brownian motion and **the** thermophoresis on **the** **heat** **transfer** characteristics. Recently, **the** analytical solutions for **the** laminar axisymmetric mixed convection boundary layer nanofluid flow past a vertical cylinder is obtained by Rashidi et al. (2012a). Stagnation point flow **of** nanofluid near a permeable stretched **surface** with thermal convective condition is provided by Alseadi et al. (2012). Mustafa et al. (2013) discussed **the** boundary layer flow **of** nanofluid **over** an exponentially stretching sheet with convective boundary conditions. Rashidi et al. (2014b) presented **the** analytical solutions **of** transport phenomena in nanofluid adjacent to a nonlinearly porous stretching sheet. Sheikholeslami and Ganji (2013a) studied **the** **heat** **transfer** **of** Cu-water nanofluid flow between **the** parallel plates. Turkyilmazoglu (2013) studied **the** unsteady mixed convection flow **of** nanofluids **over** a moving vertical flat plate with **heat** **transfer**. Sheikholeslami et al. (2013b) determined free convection flow **of** nanofluid. Hayat et al. (2014) presented **the** mixed convection peristaltic flow **of** magnetohydrodynamic (MHD) nanofluid in presence **of** Brownian motion and thermophoresis. Casson fluid model is one **of** **the** base fluids which exhibits yield stress. However such fluid behaves like a solid when shear stress less than **the** yield stress is applied and it moves if applied shear stress is greater than yield stress. Examples **of** Casson fluid include jelly, soup, honey, tomato sauce, concentrated fruit juices, blood and many others. In fact several substances like protein, fibrinogen and globin in an aqueous base plasma, human red cells form a chain like structure, known as aggregates or rouleaux. If **the** rouleaux behaves like a plastic solid then there exists a field stress that can be identified with **the** constant yield stress in Casson fluid by Dash et al. (1996). Recently, Mukhopadhyay (2013a) provided **the** boundary layer flow **of** Casson fluid **over** a non-linearly stretching sheet. Some **of** **the** recent studies about flow **of** Casson fluid are [Shehzad et al. (2013), Mukhopadhyay and Vajravelu (2013b), Hayat et al. (2012a)].

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In order to verify obtained numerical results **experimental** **investigation** was carried out. **The** experiments were conducted on **the** **experimental** installation shown in fig. 8. **The** main part was **the** cylindrically shaped tank **of** about 77 dm 3 , whose internal space in this case was filled by paraffin E53 as PCM. **The** PCM was heated by **the** electric heater (EH), located in **the** central position **of** **the** TES. Four thermocouples (A1, A2, A3, and A4) were placed at **the** heater **surface**. **The** top thermocouple (A1) at **the** heater **surface** was used for **the** heating control (**the** switch off sensor). If **the** temperature **of** **the** heater reached 473 K **the** electricity was switched off, until **the** temperature dropped below **the** given range. For **the** measurement **of** temperature profile inside PCM, eight thermocouples (B1-B4 and C1-C4) were placed in- side **the** tank, four along **the** axis and two along **the** radius. Four thermocouples (D1-D4) were placed at **the** outer **surface** **of** **the** tank. **The** enumeration and position are shown in fig. 8.

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To reduce **heat** losses from **the** **heat** exchangers to **the** environment, insulation is installed as illustrated in Fig. 1b. **The** ceramic plate is used to provide a space between **the** **heat** exchangers to prevent **the** **heat** conduction between them. Each **heat** exchanger rests on a PTFE cylinder to avoid a thermal contact with **the** stainless steel case. Pieces **of** PE sheets with 10cm length are attached to **the** internal **surface** **of** **the** stainless steel resonator pipe to reduce **heat** loss from **the** oscillating fluid to **the** pipe. Silicate wool is put in **the** cavity between **heat** exchangers and stainless steel case to reduce **the** **heat** loss due to natural convection in **the** empty volume. With these efforts, **the** **heat** losses still exist. This part **of** **heat** loss is calculated and added to **the** cold side to give **the** approximate total **heat** output. **The** **heat** imbalance between **the** **heat** input and output is used as an indication **of** **the** accuracy **of** **the** **experimental** data. In **the** present study, **the** average **heat** imbalance is 13.42%.

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Rather than Brownian motion, liquid layering, phonon transport, and agglomeration, Lee et al. (2006) experimentally investigated **the** effect **of** **surface** charge state **of** **the** nanoparticle in suspension on **the** thermal conductivity. They showed that **the** pH value **of** **the** nanofluid strongly affected **the** thermal performance **of** **the** fluid. **The** further **the** pH value diverged from **the** isoelectric point **of** **the** particles, **the** more stable **the** nanoparticles in **the** suspension and greater **the** change in **the** thermal conductivity. That may partially explain **the** disparities between different **experimental** data since many researchers used surfactants in nanofluids, but with insufficient descriptions. By adopting a variation **of** **the** classical **heat** conduction method in porous media to **the** problem **of** **heat** conduction in nanofluids, Vadasz (2006) demonstrated that **the** transient **heat** conduction process in nanofluids may provide a valid alternative explanation for **the** apparent **heat** **transfer** **enhancement**.

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It is noticed that when **the** density **of** an electrically conducting fluid is low and/or applied magnetic field is strong, Hall current plays a vital role in determining flow-features **of** **the** fluid flow problems because it induces secondary flow in **the** flow-field (Sutton and Sherman (1965). Taking into account **of** this fact, Aboeldahab and Elbarbary (2001) and Seth et al. (2012) investigated **the** effects **of** Hall current on hydromagnetic free convection boundary layer flow past a flat plate considering different aspects **of** **the** problem. It is noteworthy that Hall current induces secondary flow in **the** flow-field which is also **the** characteristics **of** Coriolis force. Therefore, it is essential to compare and contrast **the** effects **of** these two agencies and also to study their combined effects on such fluid flow problems. Narayana et al. (2013) studied **the** effects **of** Hall current and radiation- absorption on MHD natural convection **heat** and mass **transfer** flow **of** a micropolar fluid in a rotating frame **of** reference. Recently, Seth et al. (2013a) investigated **the** effects **of** Hall current and rotation on unsteady hydromagnetic natural convection flow **of** a viscous, incompressible, electrically conducting and **heat** absorbing fluid past an impulsively moving vertical plate with ramped temperature in a porous medium taking into account **the** effects **of** thermal diffusion. Aim **of** **the** present **investigation** is to study unsteady hydromagnetic natural convection **heat** and mass **transfer** flow with Hall current **of** a viscous, incompressible, electrically conducting, temperature dependent **heat** absorbing and optically thin **heat** radiating fluid past an accelerated moving vertical plate through fluid saturated porous medium in a rotating environment when temperature **of** **the** plate has a temporarily ramped profile. This problem has not yet received any attention from **the** researchers although natural convection **heat** and mass **transfer** flow **of** a **heat** absorbing and radiating fluid resulting from such ramped temperature profile **of** a plate moving with time dependent velocity may have strong bearings on numerous problems **of** practical interest where initial temperature profiles are **of** much significance in designing **of** so many hydromagnetic devices and in several industrial processes occurring at high temperatures where **the** effects **of** thermal radiation and **heat** absorption play a vital role in **the** fluid flow characteristics.

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A three dimensional incompressible steady model has been developed to investigate **the** effects **of** Reynolds number, aspect ratio, rarefaction, Prandtl number and radiation **heat** **transfer** on Poiseuille and Nusselt number for fully developed laminar flow **over** a range **of** slip flow regime in a microchannel with rhombus cross section. Constant wall temperature, slip velocity and temperature jump boundary conditions were included. **The** Nusselt and Poiseuille number both decrease with decreasing **the** value **of** aspect ratio, but rarefaction has inverse effect on Poiseuille and Nusselt number in which Poiseuille and Nusselt number decreases with increasing in Kn. It is observed from **the** figures that Reynolds number has more effect on Nusselt number then Poiseuille number. It is concluded from **the** figures and results that **the** presence **of** **the** radiation augments **the** **heat** **transfer** rate and Nusselt number to about 3% in comparison by **the** absence **of** radiation.

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A water tank **of** 40 liters capacity with two numbers **of** electrical heaters (each 2 kW capacity) with temperature monitor is used to **heat** and maintain **the** required temperature **of** hot water which is flowing in **the** shell side **of** **heat** exchanger. In order to measure **the** relative temperature **of** both hot and cold water, a digital temperature indicator is used. Four number **of** RTD were provided to measure temperature **of** hot and cold water. Two thermocouples measures hot water and two **of** them measures cold water temperatures.

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