Thermal performance of radiant floor heating systems concrete slabs

A new simplified model to calculate surface temperature and heat transfer of radiant floor heating and cooling systems

The mixed Marangoni assisting/resisting flow of a nanofluid with thermal radiative heat flux is analyzed when thermal and solutal buoyant forces are significant. The heat and mass transfer rates are simultaneously optimized by utilizing the Response Surface Methodology (RSM). The face‐centered Central Composite Design (fc‐CCD) is used for the numerical experimental design involved in RSM. The sensitivities of the heat and mass transfer rates are evaluated to compare the impact of the thermal and solutal buoyant forces. Appropriate scaling and similarity transformations are utilized to simplify the problem and then numerical solutions are obtained. The nanoliquid flow, temperature, and concentration profiles are plotted for the buoyancy assisting and opposing Marangoni cases. The Marangoni flow with opposite buoyancy is found to have a greater magnitude of velocity while the flows assisted by the buoyancy have a greater magnitude of temperature and concentration profiles. Thermal buoyancy force has a predominant (0.6%) impact on both heat and mass transfer rates compared to solutal buoyancy force. Buoyancy forces are positively sensitive to heat and mass transfer rates. The thermal radiation aspect augments the temperature profile throughout the domain. The optimized mass and heat transfer rates ( and ) is achieved at the highest level of the buoyancy forces and ratio of Marangoni numbers.

Two-dimensional heat transfer in a fin was modeled with acceptable accuracy and optimized. Bezier curve was used to estimate the fin geometry. The finite volume method coupled with the artificial neural network was developed to predict the temperature distribution through the fin with -1.5% to +1% and ± 0.5% accuracy for fin efficiency and rate of heat transfer, respectively. Locations of four control points in the Bezier curve were considered as design variables. Then, fast and elitist non-dominated sorting genetic algorithm (NSGA-II) was applied to find the maximum fin efficiency and the rate of heat transfer as two objective functions. The results of optimal designs were a set of multiple optimum solutions, called ‘Pareto optimal solutions’. The maximum 72 percent for fin efficiency was found with 739W as its rate of heat transfer while the maximum rate of heat transfer was 962.3 W with 57 percent efficiency. In addition, the optimum results of two-dimensional heat transfer were compared with one-dimensional and the average 14.7 percent decreases in fin efficiency and the rate of heat transfer was found that show the deficiency of the one-dimension modeling. In the second case study, the Pareto front was derived for the rate of heat transfer and fin surface area as two objective functions. It was observed that the results of optimum fin configuration in the case of fin efficiency as objective function are the same with the results of fin surface area as objective function.

Thermodynamic and hydraulic design characteristics of the fin tube heat exchanger

Floor radiant heating systems transfer heat energy from hot water through the floor surface into the room. Traditional systems use a dry-bulb temperature (DBT) sensor mounted on the wall, which measures only the dry-bulb temperature in its immediate vicinity. This measurement controls the temperature and flow rate of the heating water for the entire room. However, this method often results in energy inefficiencies and excessive heating, as it fails to consider the radiant heat and thermal storage of the surrounding surfaces.In response to these energy challenges, this study proposes a Mean Radiant Temperature (MRT) sensing control method and evaluates its energy performance concerning wall emissivity (wall color). An experimental study was conducted to compare MRT sensing control with Dry Bulb Temperature (DBT) sensing control under conditions of black (low emissivity) and reflective (high emissivity) walls. The experimental results were analyzed based on the time required to reach the set-point temperature, floor temperature, and energy consumption.The findings indicate that Mean Radiant Temperature (MRT) sensing control, which takes into account heat storage and the radiant heat of walls, leads to a reduced set-point temperature arrival time and lower energy consumption compared to Dry Bulb Temperature (DBT) sensing control. This effect is particularly pronounced in environments with low-emissivity black walls. These results suggest that MRT sensing control can significantly mitigate energy inefficiencies and reduce excessive heating, thereby contributing to more sustainable and efficient building heating systems.

Evaluation and comparison of thermal comfort of convective and radiant heating terminals in office buildings

A pilot scale radiant wall oven (RWO) was used to bake potato strips at 12 different time-temperature combinations within 16 min at 290°C to 6.5 min at 365°C. Radiant and overall heat transfer coefficients were experimentally determined for each RWO treatment by monitoring temperature and heat flux. Correlation between heat transfer parameters and quality of the samples was also determined. It was determined that 92%–94% of the overall heat transfer coefficient was contributed by radiant heat transfer. While no correlation was found between color of the RWO baked potato strips and heat transfer coefficients, texture of the RWO baked potato strips was negatively correlated with overall and radiant heat transfer coefficients. Radiant heating could be used as a surface treatment to bake potato strips to mimic the surface of fried strips without increasing their fat content.

Perspired moisture plays a crucial role in the thermal physiology and protection of the human body wearing thermal protective clothing. Until now, the role of continuous sweating on heat transfer, when simultaneously considering internal and external heat sources, has not been well-investigated. To bridge this gap, a sweating torso manikin with 12 thermal protective fabric systems and a radiant heat panel were applied to mimic firefighting. The results demonstrated how the effect of radiant heat on heat dissipation interacted with amount of perspired moisture and material properties. A dual effect of perspired moisture was demonstrated. For hydrophilic materials, sweating induced evaporative cooling but also increased radiant heat gain. For hydrophilic station uniforms, the increment of radiant heat gain due to perspired moisture was about 11% of the increase of heat dissipation. On the other hand, perspired moisture can increase evaporative cooling and decrease radiant heat gain for hydrophobic materials. In addition to fabric thermal resistance ( Rct) and evaporative resistance ( Ret), material hydrophilicity and hydrophobicity, emissivity and thickness are important when assessing metabolic heat dissipation and radiant heat gain with profuse sweating under radiant heat. The results provide experimental evidence that Rct and Ret, the general indicators of the clothing thermo-physiological effect, have limitations in characterizing thermal comfort and heat strain during active liquid sweating in radiant heat. This paper offers a more complete insight into clothing thermal characteristics and human thermal behaviors under radiant heat, contributing to the accurate evaluation of thermal stress for occupational and general individuals.

Numerical investigation of condensation on microstructured surface with wettability patterns

The buoyancy-driven transient double-diffusive convection in a square cavity filled with water-saturated porous medium is studied numerically. While the right and left side wall temperatures vary linearly from θa to θo and θo to θb, respectively, with height, the top and bottom walls of the cavity are thermally insulated. The species concentration levels at the right and left walls are c1 and c2, respectively, with c1>c2. The Brinkman–Forchheimer extended Darcy model is considered to investigate the average heat and mass transfer rates and to study the effects of maximum density, the Grashof number, the Schmidt number, porosity, and the Darcy number on buoyancy-induced flow and heat transfer. The finite volume method with power law scheme for convection and diffusion terms is used to discretize the governing equations for momentum, energy, and concentration, which are solved by Gauss–Seidel and successive over-relaxation methods. The heat and mass transfer in the steady-state are discussed for various physical conditions. For the first time in the literature, the study of transition from stationary to steady-state shows the existence of an overshooting between the two cells and in the average Nusselt number. The results obtained in the steady-state regime are presented in the form of streamlines, isotherms, and isoconcentration lines for various values of Grashof number, Schmidt number, porosity and Darcy number, and midheight velocity profiles. It is found that the effect of maximum density is to slow down the natural convection and reduce the average heat transfer and species diffusion. The strength of convection and heat transfer rate becomes weak due to more flow restriction in the porous medium for small porosity.

The paper attempt to investigate the effect of injection/suction on the flow of electrically conducting fluid through a porous channel filled with porous material. A magnetic field of uniform strength is applied perpendicular to the plane of the porous channel. The effect of heat radiation, heat source and chemical reaction has been taken into consideration. The governing equations are solved analytically by using complex variable notation. The expressions for velocity, temperature, concentration, skin friction coefficient, rate of heat transfer and rate of mass transfer have been obtained. The effect of various parameters entering the governing equation have been evaluated numerically and expressed graphically and in tabular form. A detailed discussion is given in the result and discussion section of the research paper.

CFD based study of fluid flow and heat transfer effect for novel turning tool configured with internal cooling channel

Heat and mass transfer rates from complex surfaces to a turbulent channel flow were measured using an infrared imaging system and the naphthalene sublimation technique, respectively. The surfaces are composed of spherical particles embedded either in a layer of thermally conducting, nonevaporating liquid or in an isothermal layer of subliming naphthalene. The experimental results indicate that, in general, the surface heat and mass transfer coefficients vary as the surface roughness increases, whereas the surface heat transfer coefficient changes as the solid-to-liquid thermal conductivity ratio is varied. Mass transfer rates exhibit less sensitivity to variations in the naphthalene height for surfaces composed of smaller particles, and heat transfer rates from surfaces of smaller particles remain fairly constant as the liquid level and thermal conductivity ratios are varied. The results are discussed relative to drying of partially wetted surfaces with surface complexity induced by the presence of droplets upon an impermeable substrate or a receding moisture front in a bed of granular material.

This communication analyzes the dual convection regime of Newtonian fluid flow in a Y shaped porous enclosure with heat and mass distribution, using a mathematical model of dimensionless PDEs and an effective finite element method. The top curved wall of the enclosure is assumed hot and side walls are cold while the bottom wall is assumed adiabatic. The problem is discretized using P2 and P1 finite element methods to approximate the displacement, pressure, and velocity. The linearized system of equations is solved using Newton’s iterative scheme. The study evaluates the impact of key parameters such as the Hartmann number, Lewis number, Rayleigh number, and buoyancy ratio on the flow, heat transfer rate, and mass transfer rate. Results indicate that an increase in the Hartmann number, Rayleigh numbers and buoyancy ratio amplifies both mass and heat transfer rates. The buoyancy ratio has a noteworthy impact on the flow and transfer rates, with a greater influence seen for. The study presents graphical representations of flow and temperature fields, as well as Nusselt and Sherwood numbers provide a comprehensive visualization of the results. Heat and mass transfer rate is minimum for concentration dominated counter flow (N=−2) and maximum for concentration dominated assisting flow N=2.

The building sector is known to make a large contribution to total energy consumption and CO2 emissions. Phase change materials (PCMs) have been considered for thermal energy storage (TES) in buildings. They can balance out the discrepancies between energy demand and energy supply, which are temporally out of phase. However, traditional PCMs need special latent storage devices or containers to encapsulate the PCM, in order to store and release the latent heat of the PCM. The proper design of TES systems using a PCM requires quantitative information and knowledge about the heat transfer and phase change processes in the PCM. In Korea, radiant floor heating systems, which have traditionally been used in residential buildings, consume approximately 55% of the total residential building energy consumption in heating. This article reviews the development of available latent heat thermal energy storage technologies and discusses PCM application methods for residential building using radiant floor heating systems with the goal of reducing energy consumption.