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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.

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.

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.

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.

During the past several years, research and studies in the field of solar energy have been continuously increased. One of the substantial applications of solar energy is related to industrial utilization for the drying process by efficient heat transfer methods. This study aims to upgrade the overall performance of an indirect solar dryer using a solar absorber extension tube (SET) equipped with ball-type turbulators.

In this work, three various SETs including hollow (SET Type 1), 6-balls (SET Type 2) and 10-balls (SET Type 3), have been simulated using Fluent software to evaluate heat transfer characteristics and flow structure along the air passage. Then, the modified solar drying system has been manufactured and tested at different configurations.

The findings indicated that adding a SET improved the performance notably. According to the results, using turbulators in the tube has a positive effect on heat transfer. The highest overall thermal efficiency was found in the range of 51.47%–64.71% for the system with SET Type 3. The maximum efficiency increment of the system was found as 19% with the use of SET. Also, the average specific moisture extraction rate, which is a significant factor to survey the effectiveness of the dehumidification system was found between 0.20 and 0.38 kg kWh⁻¹.

In the present study, a novel SET has been developed to upgrade the performance of the solar dehumidifier. This new approach makes it possible to improve both thermal and drying performances.

Over the recent years, solar energy has received outstanding attention from researchers. Solar energy applications and related large-scale projects are increasing to meet growing global energy demand as an economical, non-polluting and renewable energy source. The purpose of this study is investigating different plenum and absorber configurations of solar air heating wall (SAHW) experimentally and numerically.

In this study, various configurations of SAHW have been numerically simulated to determine the most effective design. According to the simulation results, two SAHWs with various plenum thicknesses have been fabricated and tested at different conditions.

Numerical simulation results indicated that parallel-flow SAHWs exhibited better performance in comparison with other placements of absorber plate. Regarding to the experimentally attained results, the highest thermal efficiency was reached to 80.51%. Also, the average deviation between experimentally and numerically obtained outlet temperature is 5.5%.

Considering the obtained results in the present study, designed SAHW has admissible efficiency to be used in various industrial and residential applications such as; air preheating, space heating and drying.

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.

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.

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.

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.

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.

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.

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.

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.