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The experimental performance of different heat pipe heat exchanger (HPHX) configurations using distilled water as the working fluid is reported in the present study. The three HPHX configurations in the present investigation include HPHX with single wick structure (HPHX 1), HPHX with composite wick structure (HPHX 2) and hybrid HPHX (HPHX 3) which is the combination of HPHX 1 and HPHX 2. The parameters considered for the parametric analysis of HPHX in all the three configurations are outdoor air dry bulb temperature entering the evaporator section of HPHX (OADBT), return air dry bulb temperature entering the condenser section of HPHX (RADBT), outdoor air velocity (Ve) and return air velocity (Vc). The OADBT is varied between 40 and 24 °C and the outdoor & return air velocities between 0.6 and 2.4 m/s. The parametric analysis of HPHX without evaporative cooling is studied for RADBT = 24 °C whereas RADBT is maintained at 20 °C for the parametric analysis of HPHX integrated with evaporative cooling. In comparison with HPHX without evaporative cooling, the performance of HPHX with evaporative cooling is enhanced by 17% for single wick structure (HPHX 1), 47% for composite wick structure (HPHX 2) and 59% for hybrid HPHX (HPHX 3) for OADBT = 40 °C and at Ve = Vc of 0.6 m/s. The results of the experimental analysis highlights the benefits of HPHX integrated with evaporative cooling for achieving significant energy savings in air conditioning application.

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School of Mechanical Engineering

Engineering and Technology

Heat and Mass Transfer, Springer Berlin Heidelberg

Experimental performance and parametric analysis of heat pipe heat exchanger for air conditioning application integrated with evaporative cooling

The literature review indicates that, though water has a good figure of merit, very limited information is available on the use of water as the working fluid in a horizontal heat pipe heat exchanger for air conditioning applications. This article investigates theoretical and experimental analyses of horizontal heat pipe heat exchangers for air conditioning applications using distilled water as the working fluid. This heat pipe heat exchanger study consists of 20 copper tubes of 9.5 mm outside diameter arranged in two rows with a 0.3 m evaporator length, a 0.3 m condenser length, a 0.05 m adiabatic length, and 12 fins per inch of aluminum plate fins. A comparative analysis is studied for two configurations of heat pipe heat exchangers. The first configuration of heat pipe heat exchanger consists of a single wick structure with two layers of 180 mesh of phosphor bronze wire mesh, and, in the second configuration, the heat pipe heat exchanger consists of a composite wick structure (two layers of 180 mesh and two layers of 60 mesh of phosphor bronze wire mesh). The investigations are performed only for sensible heat recovery between outdoor and return air. The experimental investigations are performed by varying the outdoor air dry bulb temperature in the range of 24°C to 40°C and return air dry bulb temperature in the range of 20°C to 24°C. The present study reveals that the amount of heat recovered by a heat pipe heat exchanger with a composite wick structure is 56% better than a heat pipe heat exchanger with a single wick structure at a higher velocity of 2.4 m/s and further improves to 88% at a lower velocity of 0.6 m/s.

Science and Technology for the Built Environment, Taylor & Francis

Theoretical and experimental investigations on horizontal heat pipe heat exchangers using a composite wick structure for heat recovery in air-conditioning systems

The heat transfer and pressure drop analysis of conical coil heat exchanger with various tube diameters, fluid flow rates and cone angles is presented in this paper. Fifteen coils of cone angles 180O (horizontal spiral), 135°, 90°, 45° and 0° (vertical helical) are fabricated and analysed with, same average coil diameter (Dm) and tube length (L) with three different tube diameter (di). The experimentation is carried out with hot and cold water of flow rate 10 to 100 lph (Re range 500 to 5000) and 30 to 90 lph respectively. The temperatures and pressure drop across the heat exchanger are recorded at different mass flow rates of cold and hot fluid. The various parameters (heat transfer coefficient (hi), Nusselt number (Nu) effectiveness (ε) and friction factor (f)) are estimated using the temperature, mass flow rate and pressure drop across the heat exchanger. The analysis indicates that, Nu and f is function of flow rate, tube diameter, cone angle and curvature ratio. Increase in tube side flow rate increases Nu, whereas it reduces with increase in shell side flow rate. Increase in cone angle and tube diameter, reduces Nu. The effects of cone angle, tube diameter and fluid flow rates on heat transfer and pressure drop characteristics are detailed in this paper. The empirical correlations are proposed to bring out the physics of the thermal aspects of the conical coil heat exchangers.

Fulltext

Thermal Science

Experimental investigation on heat transfer and pressure drop of conical coil heat exchanger with parameters tube diameter, fluid flow rates and cone angle

The three HPHX (heat pipe heat exchanger) configurations in the present investigation include HPHX with single wick structure (HPHX 1), HPHX with composite wick structure (HPHX 2) and hybrid HPHX (HPHX 3) which is the combination of HPHX 1 and HPHX 2. The experimental correlations obtained are used for investigating annual energy savings in air conditioning using HPHX integrated with and without evaporative cooling, for Indian climatic zones. A representative city for each Indian climatic zone is selected for the analysis involving sensible heat recovery between outdoor air and conditioned return air. The investigation reveals that for HPHX without evaporative cooling, HPHX 1 becomes favourable choice for cities such as Bengaluru (representing temperate Indian climatic zone), Chennai (warm and humid Indian climatic zone) and Guwahati (cold Indian climatic zone). For cities such as Ahmedabad (hot and dry Indian climatic zone), Gwalior (composite Indian climatic zone) and Chennai, the use of HPHX integrated with evaporative cooling is found more promising for HPHX 3 followed by HPHX 2, whereas for cities such as Bengaluru and Guwahati, HPHX 1 becomes the popular choice. The present research gives an insight towards the performance and selection of HPHX with different configurations, for Indian climatic zone.

Energy, Pergamon

Analysis of annual energy savings in air conditioning using different heat pipe heat exchanger configurations integrated with and without evaporative cooling

Heat pipe heat exchanger (HPHX) is an excellent device used for heat recovery in air conditioning systems. The Energy Conservation Building Code (ECBC) – Bureau of Energy Efficiency (BEE) India classifies Indian climatic zones into five categories viz., Hot and Dry (e.g. Ahmedabad, Jodhpur etc), Warm and Humid (e.g. Mumbai, Chennai etc), Composite (e.g. Nagpur, Jaipur etc), Cold (e.g. Guwahati etc) and Temperate (e.g. Bengaluru etc). The literature review indicated that very limited information is available on annual energy saving analysis of air conditioning system with HPHX for Indian climatic zones. The paper investigates the possible energy savings using HPHX for heat recovery in air conditioning system for Indian climatic zones. The analysis is carried out for total 25 Indian cities representing different climatic zones. The analysis is performed for a 6 row HPHX and assuming outdoor air quantity as 1 m3/s, return air dry bulb temperature as 23 °C and compressor power as 1 kW/TR. This paper discusses the use of HPHX only for the heat recovery application (exchange of sensible heat between fresh outdoor air and conditioned return air). The annual energy savings with HPHX for a particular city is calculated for number of hours when outdoor air dry bulb temperature exceeds 25 °C. The maximum energy saving potential is revealed for hot and dry, warm and humid and composite Indian climatic zones.

Engineering Science and Technology, an International Journal, Elsevier

Theoretical energy saving analysis of air conditioning system using heat pipe heat exchanger for Indian climatic zones

The experimental investigation on thermal analysis of conical coil heat exchanger is presented in this paper. Fifteen conical coils of different cone angles (0° (helical), 45°, 90°, 135°, 180° (spiral)), with three different tube sizes (ID × OD, 8 × 10, 10 × 12 and 12 × 15) are fabricated and analysed with, same average coil diameter (Dm = 200 mm) and tube length (L = 3 m). The experimentation is carried out with hot and cold water of flow rate 10–100 lph (Re – 500 to 5000) and 30–90 lph respectively. The observations recorded were leads to analysis the heat exchanger for heat transfer and pressure drop characteristics at different flow rate of cold and hot fluid. The various parameters (heat transfer coefficient (hi), Nusselt number (Nu) effectiveness (ε) and friction factor (f)) are estimated for the heat exchanger. The analysis indicates that, Nu and f are the functions of flow rates, tube diameter, curvature ratio and cone angle. Nu increase with increase in tube side flow rate whereas it reduces with increase in shell side flow rate, increase in cone angle and increase in tube diameter. The effects of cone angle, tube diameter and fluid flow rates on heat transfer and pressure drop characteristics are detailed in this paper. The empirical correlations are proposed to bring out the physics of the thermal aspects of the conical coil heat exchangers.

International Journal of Heat and Mass Transfer, Pergamon

Investigation on thermal analysis of conical coil heat exchanger

In the present study, an experimental investigation on thermal performance of the conical coil heat exchanger with 90 conical coil heat exchanger is reported. Three different conical coil heat exchangers of same mean coil diameter (Dm = 200 mm) with different tube diameters (di = 8, 10, 12.5 mm) are analyzed under steady state condition. The analysis is carried out for the tube side hot fluid flow range of 10–100 lph (Re = 500–5,000), while the shell side flow range of 30–90 lph. The data available from experimentation leads to evaluate heat transfer coefficients for inside and outside the tube of the conical coil heat exchanger by Wilsons plot method. The calculations are further extended to estimate Nusselt Number (Nu) and effectiveness. The empirical correlations are proposed for predicting Nu and the outlet temperatures of hot and cold fluids. The predicted empirical correlations show reasonable agreement with the experimental results within the given range of parameters.

Experimental investigation on heat transfer analysis of conical coil heat exchanger with 90 cone angle

Helical coil heat exchangers are popular because of compact structure with enhanced heat transfer coefficient by passive heat transfer enhancement technique. Due to these advantages helical coil tube heat exchangers are widely used in various applications like power plants, nuclear reactors, refrigeration and air-conditioning systems, heat recovery systems, chemical processing and food industries. The analysis of the helical coil heat exchanger with different operating and geometric parameters is presented in this paper. The analysis shows that both operating and geometric parameters are having influence on heat transfer characteristic. The analysis of heat transfer coefficient and Nusselt Number with respect to Reynolds number with different correlations and its signifence is discussed in this paper. The effect of geometric parameter on performance of helical coiled tube heat exchanger is also presented in this paper. © 2013 Praise Worthy Prize S.r.l. - All rights reserved.