A numerical analysis presented out to simulate internal forced convection and temperature distribution in helical coil tube with and without nanofluid. An ANSYS FLUENT package 14.1 commercial copy with SOLID WORK and GAMBIT software program is employed. The flow pattern and temperature distribution in helical coil tube heat exchanger is studied with and without nanofluid. Numerical work included two parts: the first is included helical coil heat exchanger with optimum curvature ratio (17). An optimum helical coil pitch has been used to study the temperature distribution and flow pattern difference along the turns without nanofluid. The second part included studying the effect of using (Oxide Titanium TiO2) nanoparticle powder with 20 nm diameter dispersed in distilled water with 0.6 % volume concentrations on the same above variables. Temperature contours showed that the temperature decreased along the coil. Also there is difference in temperature between turns. After turn nine the difference become less. The results showed enhancement in the heat flow for fluid with nanofluid compared to without nanofluid.
The present study involves experimental and computational analysis to investigate the thermal performance of modified closed wet cooling tower in perspective of first and second law of thermodynamics (analysis of energy and exergy) according to Iraqi weather. The experimental study includes design, manufacture and testing prototype of a modified counter flow forced draft closed wet cooling tower. The modification based on addition packing to the conventional closed wet cooling tower. To assess the thermal performance of cooling towera progression of tests was done at various operational and conformational parameters.The theoretical study included developed six models by an Adaptive Neuro-Fuzzy Inference System to anticipating various execution parameters of the tower including the cooling range, tower approach, thermal efficiency, cooling capacity, evaporation losses and exergy destruction. After simulating, three dimensional surface viewers obtained for future behavior of the thermal performance of cooling tower involves interactions between all operational parameters. Comparison of the output values obtained using the Adaptive Neuro-Fuzzy Inference System model and those obtained experimentally for other cases not included in the training data, indicates high compatibility with maximum percentage error of (5%).
Abstract:The purpose of the present experimental work is to investigate the performance (1 ton) refrigeration system using nano-refrigerant. Nano-refrigerant is alumina (ɣ-Al 2 O 3 ) nanopartcal with size (20-30) nm is dispersed into R-134a with volume fraction 0.01% and 0.02%. The experimental test rig consists of horizontal double tube counter flow heat exchanger fabricated of copper. The nano-refrigerant is evaporated inside the inner tube because of the heat gain from hot water passing in the annulus surrounding the inner tube. The experimental results indicate, when increasing the volume concentration of Al 2 O 3 refrigerant by 0.01% and 0.02%, the heat transfer coefficient increases by 0.54% to 1.1%. The thermal conductivity increases by 11.5% and 14.2%, respectively, while the coefficient of performance increases by 3.33% to 12%, respectively. The heat transfer rate in the refrigeration side is enhancement about 6.7% to 21.4% compared with conventional refrigerant, and the power consumption by compressor is decreased by nearly 1.6% and 3.3%, respectively.
In the present work an experimental investigation is carried out to evaluate the performance of helical coiled tube with the swirl flow device using Al2O3nanofluid.The effects of wire coil insert with different parameter on heat transfer and friction loss in the helical tube were examined with Dean number (De) ranging from 700 to 2000. The circular or square coil wire has different cross sections, insertedin the tube with different pitch. The wire coil with Al2O3 nanoparticles with a diameter of 80nm dispersed in distilled water with volume concentrations of (0.08,0.1, 0.2and 0.3 vol.% ) were used as the test fluid. The effects of Dean Number, volume concentration of suspended nanoparticles, and wire coil on heat characteristics were investigated. The results reveal that the use of tabulators leads to a considerable increase in heat transfer and friction loss over those of a smooth tube. The Nusselt number increases with increasing of Dean number and reduction in pitch of wire coil. The square type of wire coil provides slightly higher heat transfer than the circular under the same conditions. Results show that the optimum heat transfer is caused of P=15mm of wire coils. Adding nanoparticles to the base fluid causes a significant enhancement in heat transfer characteristics. The overall enhancement in heat transfer using two mechanisms simultaneously compared to using pure fluid within the smooth helical tube exceeds over 213.2% (180% spring enhancement +33.2%Al2O3). The optimum results were found to be P=15mm, φ=0. 3Al2O3 t=2mm square cross section and De=1889. Finally, empirical correlations are developed of predicting Nusselt number of the flow with and without nanofluid. Comparison between the present result in reference results show good agreement.
Experimental investigation of heat transfer enhancement in heat transfer coefficient of shell and helical coil tube heat exchanger with and without addition nanofluid is carried out in the present work. Experimental work is included two parts: the first one is included design of helical coil heat exchanger with optimum curvature ratio (17), an optimum helical coil pitch has been used to study the heat transfer coefficient without nanofluid. The second part is included studying the effect of using (Oxide Titanium TiO2) nanoparticle powder with 20 nm diameter is dispersed in distilled water with different volume concentrations (0.2, 0.4, 0.6, and 0.8) % by volume on heat transfer coefficient. The experimental results showed that, when nanofluid was used there is an increase in heat transfer coefficient and thermal conductivity by (20) %. An empirical correlation has been found to show the variation of Nusselt number with Dean number by using nano fluid with error of (±5%).
This paper presents thermal characteristics analysis of a modified Closed Wet Cooling Tower (CWCT) based on heat and mass transfer principles to improve the performance of this tower in Iraq. A prototype of CWCT optimized by added packing was designed, manufactured and tested for cooling capacity of 9 kW. Experiments are conducted to explore the effects of various operational and conformational parameters on the thermal performance. In the test section, spray water temperature and both dry bulb temperature and relative humidity of the air measured at intermediate points of the heat exchanger and packing. Heat exchangers consist of four rows and eight columns for an inline tubes arrangement and six rows and five columns for staggered tubes arrangement. According to experimental data, the inline tubes arrangement has a better thermal performance than the staggered tubes arrangement. The inline tubes arrangement enhanced thermal efficiency more than (7%) compared to the staggered tubes arrangement. Furthermore the effect of added packing to CWCT on thermal performance was significant compared to CWCT without packing. Comparing CWCT with packing, it has been observed that the best performance for the CWCT with packing under heat exchanger. It can be watched that the thermal efficiency for CWCT with packing under heat exchanger and CWCT with packing above heat exchanger approximately (28%) and (16%) higher than that CWCT without packing respectively. This study provides correlations to predict heat and mass transfer considering the influences of operational parameters for both inline and staggered heat exchanger tubes arrangement.
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