Faraz Afshari, Azim Doğuş Tuncer, Adnan Sözen, Halil Ibrahim Variyenli, Ataollah Khanlari and Emine Yağız Gürbüz
Using suspended nanoparticles in the base fluid is known as one of the most efficient ways for heat transfer augmentation and improving the thermal efficiency of various heat…
Abstract
Purpose
Using suspended nanoparticles in the base fluid is known as one of the most efficient ways for heat transfer augmentation and improving the thermal efficiency of various heat exchangers. Different types of nanofluids are available and used in different applications. The main purpose of this study is to investigate the effects of using hybrid nanofluid and number of plates on the performance of plate heat exchanger. In this study, TiO2/water single nanofluid and TiO2-Al2O3/water hybrid nanofluid with 1% particle weight ratio have been used to prepare hybrid nanofluid to use in plate type heat exchangers with three various number of plates including 8, 12 and 16.
Design/methodology/approach
The experiments have been conducted with the aim of examining the impact of plates number and used nanofluids on heat transfer enhancement. The performance tests have been done at 40°C, 45°C, 50°C and 55°C set outlet temperatures and in five various Reynolds numbers between 1,600 and 3,800. Also, numerical simulation has been applied to verify the heat and flow behavior inside the heat exchangers.
Findings
The results indicated that using both nanofluids raised the thermal performance of all tested exchangers which have a various number of plates. While the major outcomes of this study showed that TiO2-Al2O3/water hybrid nanofluid has priority when compared to TiO2/water single type nanofluid. Utilization of TiO2-Al2O3/water nanofluid led to obtaining an average improvement of 7.5%, 9.6% and 12.3% in heat transfer of heat exchangers with 8, 12 and 16 plates, respectively.
Originality/value
In the present work, experimental and numerical analyzes have been conducted to investigate the influence of using TiO2-Al2O3/water hybrid nanofluid in various plate heat exchangers. The attained findings showed successful utilization of TiO2-Al2O3/water nanofluid. Based on the obtained results increasing the number of plates in the heat exchanger caused to obtain more increment by using both types of nanofluids.
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Ataollah Khanlari, Adnan Sözen and Halil İbrahim Variyenli
The plate heat exchangers (PHE) with small size but large efficiency are compact types of heat exchangers formed by corrugated thin pressed plates, operating at higher pressures…
Abstract
Purpose
The plate heat exchangers (PHE) with small size but large efficiency are compact types of heat exchangers formed by corrugated thin pressed plates, operating at higher pressures when compared to most other traditional exchangers. This paper aims to analyze heat transfer characteristics in the PHE experimentally and numerically.
Design/methodology/approach
Computational fluid dynamics analysis has been used to simulate the problem by using the ANSYS fluent 16 software. Also, the effect of using TiO2/water nanofluid as working fluid was investigated. TiO2/water nanofluid had 2% (Wt/Wt) nanoparticle content. To improve solubility of the TiO2 nanoparticles, Triton X-100 was added to the mixture. The results have been achieved in different working condition with changes in fluid flow rate and its temperature.
Findings
The obtained results showed that using TiO2/water nanofluid improved the overall heat transfer coefficient averagely as 6%, whereas maximum improvement in overall heat transfer coefficient was 10%. Also, theoretical and experimental results are in line with each other.
Originality/value
The most important feature which separates the present study from the literature is that nanofluid is prepared by using TiO2 nanoparticles in optimum size and mixing ratio with surfactant usage to prevent sedimentation and flocculation problems. This process also prevents particle accumulation that may occur inside the PHE. The main aim of the present study is to predict heat transfer characteristics of nanofluids in a plate heat exchanger. Therefore, it will be possible to analyze thermal performance of the nanofluids without any experiment.
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Emine Yağız Gürbüz, Halil İbrahim Variyenli, Adnan Sözen, Ataollah Khanlari and Mert Ökten
Heat exchangers (HEXs) are extensively used in many applications such as heating and cooling systems. To increase the thermal performance of HEXs, nano-sized particles could be…
Abstract
Purpose
Heat exchangers (HEXs) are extensively used in many applications such as heating and cooling systems. To increase the thermal performance of HEXs, nano-sized particles could be added to the base working fluid which can improve the thermophysical properties of the fluid. In addition, further improvement in the thermal performance of nanofluids can be obtained by using two or more different nanoparticles which are known as hybrid nanofluids. This paper aims to improve the thermal efficiency of U-type tubular HEX (THEX) by using CuO-Al2O3/water hybrid nanofluid.
Design/methodology/approach
Numerical simulation has been used to model THEX with various configurations. Also, CuO-Al2O3/water hybrid nanofluid has been experimented in THEX in two various modes including parallel (PTHEX) and counter flow (CTHEX) regarding to the numerical findings. Hybrid nanofluids have been prepared in two particle concentrations and compared with CuO/water nanofluid at the same concentrations and also with water.
Findings
The numerical simulation results showed that adding fins and also using hybrid nanofluid can increase heat transfer rate in HEX. However, adding fins cannot be a good option in U-type THEX with lower diameter because it increases pressure drop notably. Experimental results of this work illustrated that using Al2O3-CuO/water hybrid nanofluid in the THEX improved thermal performance significantly. Maximum enhancement in overall heat transfer coefficient of THEX by using CuO-Al2O3/water nanofluid in 0.5% and 1% concentrations achieved as 9.5% and 12%, respectively.
Originality/value
The obtained findings of the study showed the positive effects of using hybrid type nanofluid in comparison with single type nanofluid. In this study, numerical and experimental analysis have been conducted to investigate the effect of using hybrid type nanofluid in U-type HEX. The obtained results exhibited successful utilization of CuO-Al2O3/water hybrid type nanofluid in HEX. Moreover, it was observed that thermal performance analysis of the nanofluids without any experiment can be done by using numerical method.