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Researchers in heat transfer are paying close attention to nanofluids because of their potential as high-performance thermal transport media. In light of natural convection's enormous significance, the addition of nanoparticles significantly enhances the thermophysical properties of the nanofluids compared to the base fluid. In this study, experimental work was used to evaluate the influence of CuO nanoparticles on natural convection with magnetohydrodynamic (MHD) flow in a square cavity. The cavity’s left and right vertical walls were maintained at different temperatures, and the top and bottom walls of the cavity were insulated. This experimental study applied a horizontal magnetic field with uniform strength. Results were obtained for a variety of Hartmann numbers ranging from 0–300, Rayleigh numbers going from 2.76E+8 to 6.89E+8, and solid volume fractions ranging from 0 to 1.5%Vol. Results showed that the heat transfer coefficient and Nusselt number values decreased with the increase in the values of the Hartmann number, except for the heat transfer coefficients at Ha=100 and 150 are larger than the heat transfer coefficients at Ha= 0. The maximum heat transfer coefficient and Nusselt number enhancement were 40.8% and 28.5%, respectively, at a 1.5% volume concentration of CuO-water nanofluid, Ra= 6.7E+8 and Ha=100 compared with pure fluid (water) at Ha=0.

This study aims to enhancement of heat transfer in double pipe heat exchanger by improving the thermal properties of base fluid which is water by adding AL2O3-Fe2O3 nanoparticles to the water. Al2O3-Fe2O3/water hybrid Nanofluid were examined experimentally and numerically at different flow rates ranging between (3 -7) Lpm at temperature of 25°C in an external tube while there was a hot water at a temperature of 60°C and a flow rate ranged between (3 – 5) Lpm running in the central tube of a double pipe counter heat exchanger. Also, the effect of various concentrations ranged between (0.05, 0.1, 0.15, 0.2, 0.25 and 0.3%) of Al2O3-Fe2O3 nanoparticles dispersed in water on the rate of heat transfer, friction coefficient were verified experimentally and numerically . The ratio of Al2O3-Fe2O3 is 0.5:0.5. The experimental and numerical study indicated that with the rate of heat transfer increases when the concentration of suspended nanoparticles in the base fluid increases , but on the other hand, the skin friction coefficient and pressure drop increases as well with increasing the concentration of nanoparticles. The maximum enhancement in heat transfer for AL2O3-Fe2O3 is about 6 % . The results from the experimental study were largely consistent with the numerical results.

The current study has investigated the effects of different wave amplitudes of the trapezoidal corrugated surface in a triangular microchannel on the thermal and hydraulic properties using the finite volume method. The laminar forced convection of CuO-water nanofluid, Ag-water nanofluid, and CuO-Ag/water hybrid nanofluid as working fluid over Reynolds number and nanoparticle volume fraction ranges of 5-500 and 0-0.03, respectively, has been examined. The base of the triangular channel was exposed to 25,000 W/m 2 of heat flux. The results indicate that the shape and wave amplitude have no significant effect on the behavior of streamlines at Re = 5, except in the regions of the crest of the wave where the velocity increases slightly due to the convergence section. The streamlines began to change in shape, especially at the wave amplitude of 125 m and Re above 100, while the temperatures on the corrugated surface decreased as the Reynolds number increased. Furthermore, the skin friction coefficient at Re = 5 for all wave amplitudes is about 10 times higher than the skin friction coefficient at Re = 100. In addition, the results showed that adding a small amount of Ag nanoparticles to the CuO nanofluid enhanced the thermal conductivity of the fluid and thus improved the heat transfer rate.

In this paper, numerical study has been conducted for using PCM as thermal insulation materials by incorporating it with layers of walls and ceiling of buildings. The effect of PCM and its role in improvement of thermal performance and thermal comfort is numerically studied. ESP-r software program has been used for numerical simulation in this paper. Energy plus weather database software was used to create climate date for Kut city (32.5 oN 45.8 oE) that used for simulation in this study. Two identical rooms were inserted in software ESP-r with dimensions (1.5m*1.5m*1m), the first is standard room for comparison and the second is test room for experimenting. Many cases were studied according to the thickness of the PCM and according to the orientation (North wall, South wall, East wall, West wall, and ceiling). Results obtained showed a reduction in indoor temperature of the zone and the reduction in the cooling load and as a result saving in electricity consumption with using PCM as insulation materials.

In this project, the flow distribution for air and water, and the enhancement of the heattransfer coefficient are experimentally studied. Experimental studies have been performed totest the influence of discharge, pitch, the height of ribs at a constant heat flux on thetemperature and pressure distributions. Along the channel of the test and the heat transfercoefficient, the water volume flow rate was about (5-12 L/min), the air volume flow rate wasabout (5.83-16.66 L/min), and heat were (80, 100,120, watt). An experimental rig wasconstructed within the test whole system. On the other hands, the channel has a divergentsection with an angle =15o with vertical axis. The study included changing in the ribs heightby using three values (12, 15, 18 mm) and changing the ribs pitch into three values (5, 8, 10mm).The results indicated an increasing in the local heat transfer coefficient as a result ofincreasing the discharge. While there was an inverse influence for the temperature distributionalong the test channel which drops when the discharge rise. The results also confirm that theincreasing in the pitch distance leads to reduce the heat transfer coefficient. Increasing theribs height increases the coefficient of heat transfer. However, the experiment heat transfercoefficient improves about (15.6 %) when the water volume flow rate increased from (5 to 12L/min), and about (18.7%) when the air volume flow rate increased from (5.83 to 16.66L/min). The best heat transfer coefficient was about (35.6 %) which can be achieved whenthe pitch decreased from (10 to 5mm). The increasing of the height from (12 to 18) mmimproves the heat transfer coefficient about (11.2 %). The best rib dimension was 18 mmheight, and 5 mm pitch, which give a maximum heat transfer coefficient (1212.02 W/m2. oC).

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