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American Journal of Public Health Research
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The Implementation of a Tele-Homecare System with Service Oriented Architecture and HL7 Message Transmission Standard
Ching-Sung Wang

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The Influence of Ethanol on Pyruvate Kinases Activity in Vivo, in Vitro, in Silico
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Clinical and Histological Features in Wegener Granulomatosis
Li Cavoli Gioacchino, Passantino Rita, Bono Luisa, Tortorici Calogera, Ferrantelli Angelo, Giammarresi Carlo, Rotolo Ugo

American Journal of Infectious Diseases and Microbiology
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The Curse of Lymphatic Filariasis: Would the Continual Use of Diethylcarbamazine Eliminate this Scourge in Papua New Guinea?
Anne Lanham, Lillian Mwanri

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Investigation of Metal and Metal Oxide nanocoating on Fins in HPHE with Silver Water NanoFluid

Aysar A. Alamery*, Zainab F. Mahdi, Hussein A. Jawad

Institute of laser for postgraduate studies, University of Baghdad, Iraq

Abstract: An improvement of energy saving and the heat transfer characteristics via introducing nanocoating of fins is a new method in HVAC systems. ANSYS software is the preferred choice to design a model for nanocoating on fins in Thermosyphon Heat Exchangers. The investigation of thermal resistance and temperature distribution are presented. The influence of enhancing the working system is examined using different nanocoating metal and metal oxide materials of fins (Ag, Cu, AL, BeO, Al₂O₃ and CuO) in heat pipe. The effect of Nanocoating by metals is explored in which the maximum improvement occurred at the evaporator section in transient operation condition with 71.9585 for AL, 71.383 for Cu and 70.708 for Ag while, the effect of Nanocoating by metal oxide is (73.79 for CuO, 73,41 for AL₂O₃ and 71.96 for BeO). The obtained results showed that the best nanocoat material for this purpose is the aluminum for metals and copper oxide for metal oxides. The calculations give important indication that using the nanocoating just in the evaporator section to reduce the cost. The large amount of heat transfer occur in the evaporator section according to the result of thermal resistance in this section then large benefit of latent heat of the air is guiding to increase the energy saving when using HPHE in HVAC systems.

Keywords: HVAC, HP (Thermosyphone) HE,ANSYS, Nanocoat, temperature distribution, Thermal resistance

Received November 19, 2014; Revised February 20, 2015; Accepted February 26, 2015

Citation: Aysar A. Alamery, Zainab F. Mahdi, Hussein A. Jawad, Investigation of Metal and Metal Oxide nanocoating on Fins in HPHE with Silver Water NanoFluid. American Journal of Mechanical Engineering, 3 (1). 21-25. January 2015. doi:10.12691/ajme-3-1-4

1. Introduction

Heat pipes have been utilized in heat transfer related applications for many years. Depending on their application area, they can operate over a wide range of temperatures with a high heat removal capability [1]. Heat pipes are heat transfer devices which use the principles of thermal conduction and latent heat of vaporization to transfer heat effectively at very fast rates [2]. It is essentially a passive heat transfer device with an extremely high effective thermal conductivity [3] and very efficient for the transport of heat with a small temperature difference via the phase change of the working fluid [4]. The two-phase heat transfer mechanism results in heat transfer capabilities from one hundred to several thousand times that of an equivalent piece of copper [3]. Key factors affecting on thermal performance of a HPHE are: velocity, relative humidity (RH) and dry-bulb temperature (DBT) of input air, type and filling ratio (FR). Heat pipe technology has found increasing applications in enhancing the thermal performance of heat exchangers in microelectronics, energy saving in HVACs [5]. It can be used for operating rooms, surgery centers, hotels, cleanrooms etc, temperature regulation systems for the human body and other industrial sectors and are passive components used to improve dehumidification by commercial forced-air HVAC systems. They are installed with one end upstream of the evaporator coil to pre-cool supply air and one downstream to re-heat supply air. This allows the system's cooling coil to operate at a lower temperature, increasing the system latent cooling capability. Heat rejected by the downstream coil reheats the supply air, eliminating the need for a dedicated reheat coil. Heat pipes can increase latent cooling by 25-50% depending upon the application. [6]. P.G. Anjankar and Dr.R.B.Yarasu. (2012) [7] studied the new design and thermal performance of thermosyphon. W. Srimuang et al. (2012) [8] presented the knowledge of two-phase closed thermosyphon (TPCT) as being used nowadays and the application of TPCT to air to air heat exchanger. H.A. Mohammed et al. (2013) [9] studied numerically the effect of using louvered strip inserts placed in a circular double pipe heat exchanger on the thermal and flow fields utilizing various types of nanofluids.

The major aim is to examine the combined internal (heat pipe) and external (fin surface) effects of HPHE when Nanocoating materials of metal and metal oxide are done.

2. Modeling of Heat Pipe Heat Exchanger

The simulation of the heat pipe is achieved from the real design [10]. Dimensions of the model for the heat pipe were constructed in ANSYS _Pre_ prossor package [11].

The top and bottom layers are represented by the nanocoating, Six nanocoating with metal and metal oxide materials (Ag, Cu, AL, BeO, Al₂O₃, CuO) of fins respectively with their thermophysical properties [12,13]. These nanoparticles are used in coating with the aim of improving the thermal properties of the base metal (aluminum).

3. Boundary Conditions

The Boundary condition of the tube is used as temperature distribution along HP which can be obtained by phase change properties from liquid (sliver water nano fluid) in evaporator section to the vapor in the condenser section) [14]. Boundary condition of the thermal model were specified as surface loads through ANSYS codes [11]

4. Results and Discussion

The results which approach from the Ansys program after modeling the heat pipe are shown in Table 1. For All tested fins, two fixed positions were taken in evaporator according to the direction of air flow.

Table 1. Temperature distribution results which approach from the Ansys program when the program in steady and transient conditions of operation runs after the modeling of the heat pipe with all selected materials

To investigate the influence of nanocoating on fins of heat pipe performance, all the thermal resistances were determined for the evaporator and condenser sections separately and the sum was considered as the total thermal resistance of the heat pipe. The respective average temperature of evaporator and condenser are recorded to calculate the system thermal resistance. Results in Figure 1 show the decrease of the thermal resistance along the evaporator section and it becomes zero in the adiabatic section after that a small increase occurs in the condenser section compared with the evaporator section this what made the large amount of heat transfer occur in the evaporator section compared with condenser.

Figure 2 Show temperature distribution of two selected positions on fins (with and without metal nanocoating materials) in the evaporator and condenser section with the and. From these figures the results observed the small effect of nanocoat in decrease thermal resistance in the evaporator section while the large effect was observed in the condenser section with the steady and transient operation conditions. Gradual decreasing For AL but fast decreasing of R for other types of nanocoating metals.

Figure 1. Thermal resistance a long heat pipe with metal and metal oxide nanocoating materials

Figure 2. A,B Temperature distribution in two selected positions on fins (with and without metal nanocoating materials)in the evaporator section with the. A-Evaporator in steady state conditions. B- Evaporator in transient conditions

Figure 2. C,D Temperature distribution in two selected positions on fins (with and without metal nanocoating materials)in the condenser section with the. C-Condenser in Steady State Conditions. D-Condenser in Transient Conditions

After calculations of the percentages of thermal performance enhancement with nanocoating layers by using the equation ((Without Nanocoat-With Nanocoat)/(Without Nanocoat))*100 the results were arranged in Table 2. As observed from the values the using of nanocoat were successful in the evaporator section especially in transient case of operation which is the fact and the aluminum is the best metal.

Table 2. Percentages of thermal performance enhancement with metals nanocoating layers

Figure 3 Show temperature distribution of two selected positions on fins (with and without metal oxide nanocoating materials) in the evaporator and condenser section with the Re and Rc. From these figures the results observed the negative effect of nanocoat in decrease thermal resistance in the evaporator section when the HPHE operate in the steady state conditions. The small effect in decrease thermal resistance was observed in the evaporator section with transient operation conditions. In condenser section for both conditions of operation, gradual and early decreasing For all types of nanocoating metal oxides compared with fins without nanocoat.

Figure 3. A,B Temperature distribution in two selected positions on fins (with and without metal oxide nanocoating materials) in the evaporator section with the Re. A-Evaporator in steady state conditions. B- Evaporator in transient conditions

Figure 3. C,D Temperature distribution in two selected positions on fins (with and without metal oxide nanocoating materials) in the condenser section with the. C-Condenser in Steady State Conditions. D-Condenser in Transient Conditions

Table 3. Percentages of thermal performance enhancement with metal oxide nanocoating layers

After calculations of the percentages of thermal performance enhancement with nanocoating layers by using the equation ((Without Nanocoat-With Nanocoat)/(Without Nanocoat))*100 the results were arranged in Table 3. As observed from the values the using of metal oxide nanocoat were successful in the evaporator section especially in transient case of operation and copper oxide is the best one.

5. Conclusions

To improve the thermal conductivity of heat pipes coat fins by nano materials, The effective surface area of heat flux absorbent should be increased and increasing the effective thermal conductivity of the fluid. The thermal performance of fins coating by nano metal and metal oxide materials is investigated by ANSYS software, The effect of Nano coating on temperature distribution on the fins were explored in which the maximum enhancement occurred at the evaporator section in transient operation condition with 71.9585 for AL, 71.383 for Cu and 70.708 for Ag. While The effect of Nano coating by metal oxide on temperature distribution on the fins were explored in which the maximum enhancement occurred at the evaporator section in transient operation condition too with (73.79 for CuO, 73,41 for AL₂O₃ and 71.96 for BeO). The best nanocoat material for this purpose is the aluminum for metals and copper oxide for metal oxides especially in transient case of operation.

References

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[5]   | E. Firouzfar, M. Soltanieh, S. H. Noie and M. H. Saidi, “Investigation of heat pipe heat exchanger effectiveness and energy saving in air conditioning systems using silver nanofluid”, Int. J. Environ. Sci. Technol. 9: 587-594.
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