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The purpose of this paper is to investigate numerically the influence of variable fluid viscosity on thermal characteristics of plate heat exchangers for counter‐flow and steady‐state conditions.

The approach to fulfill the purpose of the paper is to derive the one‐dimensional energy balance equations for the cold and hot streams in the adjacent channels of a plate heat exchange composed of four corrugated plates. A finite difference method has been used to calculate the temperature distribution and thermal performance of the exchanger. Water is used as the hot liquid being cooled in the side channels, while a number of working fluids whose viscosity variation versus temperature is more severe were used as the cold fluid being heated in the central channel.

The program is run for a combination of working fluids such as water‐water, water‐isooctane, water‐benzene, water‐glycerin and water‐gasoline. The temperature distributions of both streams have been plotted along the flow channel for all the above combination of working fluids. The overall heat transfer coefficients have also been plotted against both cold and hot fluid temperatures. It is found that the overall heat transfer coefficient varies linearly with respect to either cold or hot fluid temperature within the temperature ranges applied in the paper. The exchanger effectiveness is not significantly affected when either the temperature dependent viscosity is applied or the nature of cold liquid is changed.

This paper contains a new method of numerical solution of energy balance equations for the thermal control volumes bounded by two plates. A comparison of the calculated results with documented experimental results validates the numerical method.

Metal additive manufacturing is an inherently thermal process, with intense localised heating and for sparse lattice structures, often rapid uneven cooling. Thermal effects influence manufactured geometry through residual stresses and may also result in non-isotropic material properties. This paper aims to increase understanding of the evolution of the temperature field during fabrication of lattice structures through numerical simulation.

This paper uses a reduced order numerical analysis based on “best-practice” compromise found in literature to explore design permutations for lattice structures and provide first-order insight into the effect of these design variables on the temperature field.

Instantaneous and peak temperatures are examined to discover trends at select lattice locations. Insights include the presence of vertical struts reduces overall lattice temperatures by providing additional heat transfer paths; at a given layer, the lower surface of an inclined strut experiences higher temperatures than the upper surface throughout the fabrication of the lattice; during fabrication of the lower layers of the lattice, isolated regions of material can experience significantly higher temperatures than adjacent regions.

Due to the simplifying assumptions and multi-layer material additions, the findings are qualitative in nature. Future research should incorporate additional heat transfer mechanisms.

These findings point towards thermal differences within the lattice which may manifest as dimensional differences and microstructural changes in the built part.

The paper provides qualitative insights into the effect of local geometry and topology upon the evolution of temperature within lattice structures fabricated in metal additive manufacturing.

At present, electrical heating clothing is widely used to keep ourselves warm at low temperature. The purpose of this paper is to explore the heat transfer performance of electrical heating fabric and the thermal comfort of human skin at low temperature.

The combined model of skin-electrical heating fabric system was established to simulate human skin tissue wearing electrical heating clothing. A series of simulation experiments are designed on the basis of verifying the effectiveness of the combined model. The temperature distribution inside the combined model and on the skin surface under different heating powers is simulated and analyzed. At the same time, the influence of ambient temperature on the thermal performance of electrical heating fabric was explored.

The skin model with blood vessels reflected the temperature change of human skin wearing electrical heating clothing. The higher the heating power of the electrical heating fabric was, the greater the temperature of the skin surface changed, the faster the temperature rose and the longer the time required to reach the stable state would be. After the heating element was electrified, it had the greatest effect on the average temperature of the epidermis and dermis, had smaller effect on the average temperature of subcutaneous layer and had little effect on the temperature of blood vessels. When the heating power was the same, the higher the ambient temperature was, the more obvious the heating effect of electrical heating fabric was. Electrical heating fabrics with different heating powers were suitable for different ambient temperature ranges.

A reasonable and effective evaluation method for the thermal comfort of electrical heating fabric was provided by establishing the skin model and combined model of the skin-electrical heating fabric system. It provides a reference for the design and application of electrical heating clothing.

The problem of natural convection in two cavities separated by an anisotropic central solid wall is considered numerically. When the thermal conductivity of the central wall is anisotropic, heat flux and temperature gradient vectors are no longer coincidence. This apparently has interesting influences on the heat and fluid flow patterns in this system. The paper aims to discuss these issues.

In this work, several flow patterns have been investigated covering a wide range of Rayleigh number up to 108. Several thermal conductivity anisotropy scenarios of the central wall have been investigated including 0, 30, 60, 120 and 150° principal anisotropy directions. The governing equations have been solved using control volume approach.

Probably the most intriguing is that, for some anisotropy scenarios it is found that the temperature at the same elevation at the side of the central wall which is closer to the colder wall is higher than that at the side closer to the hot wall. Apparently this defies intuition which suggests the reverse to have happened. However, this behavior may be explained in light of the effect of anisotropy. Furthermore, the patterns of streamlines and temperature fields in the two enclosures also changes as a consequence of the change of the central wall temperatures for the different anisotropy scenarios.

This work discusses a very interesting topic related to heat energy exchange among two compartments when the separating wall is anisotropic. In some anisotropy scenarios, this leads to more uniform distribution of Nusselt number than the case when the wall is isotropic. Interesting patterns of natural convection is investigated.

To study quantitatively the effects of combined temperature dependent thermodynamics and transport fluid properties on the heat transfer rate, heat function fields and profiles in a fluid filled square enclosure.

Navier‐Stokes equations in two‐dimensions, which are the flow governing equations, were transformed into stream function and vorticity transport equations. These equations together with the energy and heat function equations were cast into their non‐dimensional forms. Numerical solutions of the resulting equations were done by the use of finite‐difference method.

The numerical investigations conducted covered the Rayleigh and Prandtl numbers in the range 10³≤Ra≤10⁶ and 0.01≤Pr≤450, respectively, and expansion parameter ε=(T_h−T_c)/T_R in the range 0.05≤ε≤1. Results show that Boussinesq‐approximation is not sufficient to simulate natural convective flow when the difference between T_h and T_c is high and close to the reference state temperature. The effects of the other fluids properties other than density can be disregarded in computation without significant loss of accuracy. Combined fluid properties have very strong effects on the heat transfer, heat function fields and profiles.

The results of this study will serve as baseline information to designers of heat transfer or process equipment in which fluid at very high temperature occurs.

The aim of this paper is to formulate and analyze thermophoresis effects on mixed convection heat and mass transfer from vertical surfaces embedded in a saturated porous media with variable wall temperature and concentration.

The governing partial differential equations (continuity, momentum, energy, and mass transfer) are written for the vertical surface with variable temperature and mass concentration. Then they are transformed using a set of non‐similarity parameters into dimensionless form and solved using Keller‐box method.

Many results are obtained and a representative set is displaced graphically to illustrate the influence of the various physical parameters. It is found that the increasing of thermophoresis constant or temperature differences enhances heat transfer rates from vertical surfaces and increases wall thermophoresis velocities; this is due to favorable temperature gradients or buoyancy forces. It is also found that the effect of thermophoresis phenomena is more pronounced near pure natural convection heat transfer limit, because this phenomenon is directly temperature gradient‐ or buoyancy forces‐dependent.

The predicted results are restricted only to porous media with small pores due to the adoption of Darcy law as a force balance.

The paper explains the different effect of thermophoresis on forced, natural and mixed convection heat, and mass transfer problems. It is one of the first works that formulates and describes this phenomenon in a porous media. The results of this research are important for scientific researches and design engineers.

Variable density flows play an important role in many technological devices and natural phenomena. The purpose of this paper is to develop a robust and accurate method for low Mach number flows with large density and temperature variations.

Low Mach number approximation approach is used in the paper combined with a predictor-corrector method and accurate compact scheme of fourth and sixth order. A novel algorithm is formulated for the projection method in which the boundary conditions for the pressure are implemented in such a way that the continuity equation is fulfilled everywhere in the computational domain, including the boundary nodes.

It is shown that proposed implementation of the boundary conditions considerably improves a solution accuracy. Assessment of the accuracy was performed based on the constant density Burggraf flow and for two benchmark cases for the natural convection problems: steady flow in a square cavity and unsteady flow in a tall cavity. In all the cases the results agree very well with exemplary solutions.

A staggered or half-staggered grid arrangement is usually used for the projection method for both constant and low Mach number flows. The staggered approach ensures stability and strong pressure-velocity coupling. In the paper a high-order compact method has been implemented in the framework of low Mach number approximation on collocated meshes. The resulting algorithm is accurate, robust for large density variations and is almost free from the pressure oscillations.

Water damage is a severe problem in modern construction, causing economic loss and health implications. By using the patented Air Gap Method inside building constructions, harmful water in the construction can be dried out. The method drains and ventilates air gaps inside walls and floors with an airflow driven by thermal buoyancy caused by a heating cable in vertical air gaps. This paper aims to investigate this method and measurements of airflow inside air gaps of walls.

This study investigates the measured correlation between the power of the heating cable, the difference of temperature inside and outside the air gap, and the airflow. Data are collected by experimentation with a full‐scale constructed wall.

The study finds that airflow increases with raised temperature difference between the air gap and room and with raised power of the heating cable. The measured airflow reaches values up to 140 m³/metre wall and day for one cable. A small increase in temperature, between 0.2 and 0.3 ^oC inside the vertical air gap results in an air flow of approximately 60 m³/metre wall and day. The air change rate per hour for the air inside the wall construction varies between 15 times for a 6 W/m cable and 37 times for a 16 W/m cable.

The method provides the means to build houses in a more robust way, minimising the negative effects of water damage. This investigation provides an understanding of how temperature and ventilation are related in this method of construction.

The issue of ventilated construction is rarely investigated in scientific research.

The purpose of this paper is to study thermophoresis particle deposition and thermal radiation interaction on natural convection heat and mass transfer by steady boundary layer flow over an isothermal vertical flat plate embedded in a fluid saturated porous medium.

The governing partial differential equations are transformed into non‐similar form by using special transformation and then the resulting partial differential equations are solved numerically by using an implicit finite difference method.

Different results are obtained and displaced graphically to explain the effect of various physical parameters on the wall thermophoresis deposition velocity and concentration profiles. It is found that the increasing of thermal radiation parameter or dimensionless temperature ratio heats the fluid and decreases temperature gradients near permeable wall, which increases local Nusselt numbers and decreases wall thermophoresis velocities. It is also found that the effect of power indices of either temperatures or concentration enhances both local Nusselt numbers and wall thermophoresis velocities. Comparison with previously published work in the limits shows excellent agreement.

The paper presents useful conclusions based on graphical results obtained from studying numerical solutions for thermophoresis‐thermal radiation heat and mass transfer interaction by steady, laminar boundary layer over a vertical flat plate embedded in a porous medium.

The effect of the tube wall heat conduction on the natural convection in a tilted long cylindrical envelope with constant, but different temperature of the two ends and an adiabatic outer surface was numerically investigated. The envelope is supposed to be a simplified model for the pulse tube in a pulse tube refrigerator when the pulse tube is positioned at different orientations. It is found that the cylindrical envelope lateral wall heat conduction can enhance the heat transfer from the hot end to the cold end, not only because of the increase in pure heat conduction in the wall, but more importantly, also the intensification of the natural convection within the enclosure. This enhancement is resulted from the big temperature difference between the tube wall and the adjacent fluid near the hot and cold ends. Adoption of low thermal conductivity tube can effectively reduce such additional heat transfers from hot to cold end, thus reducing the loss of cooling capacity for the pulse tube refrigerator.