One-dimensional Steady-state Heat Transfer Research Articles

Simulation Study of Thermal Performance on the Inner and Outer Surfaces of Semi-Transparent Photovoltaic (STPV) Glass with Different Transparency

This paper used the experimentally verified one-dimensional steady-state heat transfer numerical model of the semi-transparent photovoltaic (STPV) glass to simulate the influence of wind speed, ambient temperature and air gap thickness on the surface temperature of PV modules, and analyzed the thermal performance of the inner and outer surfaces of STPV glazing with different transparency. Results shows that for every 1m/s increase in wind speed, the outer surface temperatures of SL-STPV glass with transparency of 10%, DL-STPV glass with transparency of 20% and 40% decreased by 3 °C, 3.02 °C and 2.22 °C, respectively. For every 10 °C increase in ambient temperature, the outer surface temperatures of SL-STPV glass with transparency of 10%, DL-STPV glass with transparency of 20% and 40% increase by 8.45 °C, 7.6 °C, and 7.79 °C, respectively. For the DL-STPV glass with transparency of 20% and 40%, for every 2 mm increase in the thickness of the air gap, the outer surface temperature increases by 0.13 °C and 0.12 °C, respectively. The heat transfer between the inner surface of the glass and the indoor environment increases the heat gain through the glass into the room in summer, which will lead to an increase in refrigeration energy consumption. However, in winter, the heat exchange between the inner surface and the in-door air to heat the indoor air reduces the heating energy consumption to a certain extent, and achieves the effect of building energy conservation to a certain extent.

Low cost energy-efficient preheating of battery module integrated with air cooling based on a heat spreader plate

Integration of heating and cooling functions has aroused increasing interest for the automotive battery modules. The proposed cylindrical 18650 battery module is equipped with an external sleeved spreader plate (SHSP), which features low thermal resistance and a large exchange area as an efficient heat transfer medium. The transient temperature characteristics of the battery module were experimentally investigated in both cooling mode and heating mode, respectively. In cooling mode, the temperature characteristics of the battery module equipped with SHSP were examined. With an inlet velocity of 1 m/s and a discharge rate of 3 C, the temperature rise and temperature difference are only 12.9 °C and 2.83 °C at an ambient temperature of 25 °C, respectively. In heating mode, the heat-up characteristics of the battery module were experimentally examined at a subzero temperature of −20 °C under three different heating protocols: continuous heating, fast-rest-slow heating, and slow-rest-fast heating. Immune from potential effects on the battery internal degradation, the heating rate of the battery module in a continuous heating protocol could reach 6.98 °C/min with a heating efficiency of 69.8%, which outperforms the existing external heating modes.Additionally, the fast-rest-slow heating protocol has clear-cut advantages in terms of heating rate while maintaining a smaller temperature difference during the heating phase. Finally, a simplified thermal resistance network model for the cell is established based on the analysis of the one-dimensional steady state heat transfer. According to projections, the thermal resistance of the present heating model is 2.03 K/W, which is less than the hot air convection heating model by 5.24 K/W. The proposed method exhibits excellent performance and provides a low-cost, highly efficient design solution for the battery module under varying conditions.

Application of Smart Phone in On-Site Test of Heat Transfer Coefficient of Building Envelope

With the increasing demand for on-site test of heat transfer coefficient of building envelope, a new test method is proposed aiming at the problems of common detection methods. According to the one-dimensional steady-state heat transfer theory of the envelope structure, the formula for calculating the heat transfer coefficient of the building envelope is derived based on the air temperature on both sides of the enclosure, the inner surface temperature and the inner surface heat transfer resistance. After turning the formula into a calculation program and loading the program into a smart phone, the heat transfer coefficient at the corresponding position can be obtained as long as the corresponding temperature and surface heat transfer resistance are input into the program. Comparing with the existing on-site detection methods of heat transfer coefficient and analyzing the detection results, it can be seen that the heat transfer coefficient obtained by this detection method is reliable, and that the method meets the needs of engineering detection. It is an economical, convenient, fast and reliable detection method to test the heat transfer coefficient of building envelope using smart phone and thermo detector.

Research on heat transfer mechanism and performance of a novel adaptive enclosure structure based on micro-channel heat pipe

In this paper, a novel adaptive enclosure structure (AES) combining the building wall and heat pipe is proposed for building wall energy saving. The theoretical heat transfer process of the structure is analyzed, and its heat transfer performance is obtained. The theoretical thermal resistance of the structure is about 0.165 K/W. The one-dimensional steady-state heat transfer experiment has been carried out. Under the temperature difference of 35 °C, the surface temperature of the AES is much higher than that of the traditional wall on the heating demand side (about 9.5 °C). The heat transfer experiment under the influence of multiple factors has been carried out. Under heating demand, the indoor side surface temperature of the AES is higher than that of the traditional wall (about 1.5 °C). Under cooling demand, the indoor side surface temperature of the structure is lower than that of the traditional wall (about 0.8 °C). In addition, it is realizable to switch the performance of the AES between efficient heat transfer or good thermal insulation according to requirements. The proposed structure has great potential for reducing the indoor energy consumption and improving thermal comfort, and could provide a new solution for passive energy-saving technology based on building envelope.

Thermal performance of a microchannel primary surface recuperator for portable microturbine generators: Design and experimental study

The recuperator with high compactness and power/weight ratio is a mandatory component of portable microturbine generators (PMTG) to achieve the required energy density and power density. In order to explore the application prospects of cross-wavy primary surface recuperators (CW-PSR), an annular microchannel CW-PSR with heat transfer matrix compactness up to 2428 m2/m3 was designed by an in-house one-dimensional steady-state heat transfer model and successfully manufactured. Furthermore, an experimental system consisting of gas and air flow paths was built to validate the developed model and investigate the thermal performance of the new CW-PSR. On this basis, heat transfer experiments were performed under steady-state by changing the mass flow rate and inlet temperature of the gas. The experimental results show a good agreement between modeled results and experimental data of the power/weight ratio and effectiveness within an error of ±2%. There exists a significant heat transfer non-uniformity in the radial direction of the CW-PSR, but it was found to have little impact on the design accuracy of overall thermal performance. Due to corrugated microchannels, the heat transfer performance of the developed CW-PSR has been enhanced by up to 113.3% compared with straight channels and the experimental power/weight ratio of the CW-PSR is in the range between 9.6 kW/kg and 16.1 kW/kg, which means the microchannel CW-PSR is a promising heat exchanger for the PMTG.

Comparative enviro-economic assessment and thermal optimization of two distinctly designed and experimentally validated PV/T collectors

This article evaluates and compares the enviro-economic potential of two distinctly (parallel flow and serpentine flow) fabricated PV/T water heating systems in view of their respective thermal optimization. A one-dimensional steady-state heat transfer model along with the concept of least entropy production yields around 20 lh−1 being the optimal flow which corresponds to highest thermal exergy of 1.5 and 1.8% for the two systems under consideration. The modeling results reveal an appreciable validation with the experimental data which correspond to maximum increment in DC power by 17.7 and 19.3 W complimented by their low-grade water heating applications worth 493.5 and 530.8 W, respectively. The mitigation potential of both the systems is well appreciated through certain pre-defined parameters as an outcome of the economic modeling. An additional 35–40% increment in total efficiency corresponds to almost 7–8% gain in electrical power with respective (parallel and serpentine) thermal configurations. Both the systems unanimously contribute 15 and 18% increment in their respective exergy-based mitigation potential as compared against 85 and 97% increment in energy-based enviro-economic parameter with respect to solo PV installation. Exergy-based performance indices show smaller increment with respect to energy-based EPI for both the designs, while energy payback period of the serpentine-based thermal installation falls 3 years shorter than a standard 255-W reference PV module.

Characterization of a new total heat recovery system using CaCl2 as working fluid: Thermal modeling and physical analysis

• A new type of heat pump system is proposed. • The variation trend of three working medium in absorber is analyzed. • The rise of flue gas temperature can reduce the harmful substances by more than 50%. • The advantages of the system compared with LiBr absorption heat pump are analyzed. This paper introduces a kind of open cycle absorption heat wet flue gas heat recovery system, which use CaCl 2 as the working medium. The system will use the wet heat recovery method and combined with an efficient heat pump system for flue gas as a heat source generator. Through direct contact with the solution in the absorber, the flue gas is going to carry out gas, liquid heat transfer between heat exchanger, realization of sensible heat and latent heat step by step. As the key part of the system, absorber is established by one-dimensional steady-state heat transfer and mass transfer model. This paper uses the finite difference method to model the discrete numerical methods, and analyzes the characteristics of heat and mass transfer in the absorber. We obtain the concentration curves of the three kinds of working medium's temperature and flow along the height direction. We also analyze the influence of CaCl 2 solution parameters changes on the absorption process, parsing the reason of the temperature change by analyzing the three working medium's energy flow trend. We found that the temperature change of flue gas is non-monotonic, which decreases gradually in the range of absorption tower height 0–0.9 m, and then increases gradually. The reason for this change is that sensible heat exchange and latent heat exchange exist between flue gas and solution. Although such a change has an impact on the efficiency of the system, it prevents the "white smoke" from condensing in the air, which effectively protects the environment. Compared with conventional LiBr absorption heat pump, the system constructed in this paper has certain advantages in latent heat recovery, flue gas heat energy utilization, energy conservation and emission reduction and economy.

Optimum Tilt Angle and Orientation of Photovoltaic Thermal System for Application in Greater Toronto Area, Canada

We present a study conducted to obtain optimum tilt angle and orientation of a solar panel for the collection of maximum solar irradiation. The optimum tilt angle and orientation were determined using isotropic and anisotropic diffuse sky radiation models (isotropic and anisotropic models). The four isotropic models giving varying optimum tilt angles in the range of 37 to 44°. On the other hand, results of the four anisotropic models were more consistent, with optimum tilt angles ranging between 46–47°. Both types of models indicated that the collector tilt should be changed four times a year to receive more solar radiation. The results also indicate that the solar panel should be installed with orientation west or east of due south with a flatter tilt angle. A 15° change in orientation west or east of due south results in less than 1% reduction of the total solar radiation received. For a given optimum tilt angle, the effect of photovoltaic/thermal (PV/T) orientation west or east of due south on the outlet temperature was determined using a one-dimensional steady state heat transfer model. It was found that there is less than 1.5% decrease in outlet temperature for a PV/T panel oriented up to 15° east or west of due south from March to December. This result indicates that existing roofs with orientations angles up to 15° east or west of due south can be retrofitted with a PV/T system without changing the roof shape.

Analysis on the Calculating of Air Leakage Threshold which Caused the Condenser Vacuum Deterioration

There is an air leakage threshold under certain condenser heat load and air ejector output. When the amount of air leakage is less than the threshold, the condenser pressure is essentially the same, we can maintain a stable condenser vacuum, once exceed the threshold, condenser pressure begin to gradually larger, condenser vacuum will deteriorate. Considered the air leakage influences on the heat transfer coefficient of condenser, this paper had been established the one-dimensional steady-state heat transfer model of condenser to obtain the condenser pressure curve along with the amount of air leakage, the turning point on the curve is the air leakage threshold.

Applicability of Heat Mirrors in Reducing Thermal Losses in Concentrating Solar Collectors

Abstract In the present work, a novel parabolic trough receiver design has been proposed. The proposed design is similar to the conventional receiver design except for the envelope and the annulus part. Here, a certain portion of the conventional glass envelope is coated with Sn-In2O3 and also Sn-In2O3 coated glass baffles are provided in the annulus part to reduce the radiative losses. The optical properties of the coated glass are such that it allows most of the solar irradiance to pass through, but reflects the emitted long wavelength radiations back to the absorber tube. Sn-In2O3 coated glass is referred to as “transparent heat mirror.” Thus, effectively reducing the heat loss area and improving the thermal efficiency of the solar collector. A detailed one-dimensional steady-state heat transfer model has been developed to predict the performance of the proposed receiver design. It was observed that while maintaining the same external conditions (such as ambient/initial temperatures, wind speed, solar insolation, flow rate, and concentration ratio), the heat mirror-based parabolic trough receiver design has about 3–5% higher thermal efficiency as compared to the conventional receiver design. Furthermore, the heat transfer analysis reveals that depending on the spatial incident solar flux distribution, there is an optimum circumferential angle (θ = θoptimum, where θ is the heat mirror circumferential angle) up to which the glass envelope should be coated with Sn-In2O3. For angles higher than the optimum angle, the collector efficiency tends to decrease owing to increase in optical losses.

Nonlinear dynamic responses of fiber-metal laminated beam subjected to moving harmonic loads resting on tensionless elastic foundation

Abstract The nonlinear dynamic responses of the fiber-metal laminated beam resting on a tensionless elastic foundation and subjected to a moving harmonic load and thermal load are investigated in the paper. The beam-foundation interaction force that only reacts in compression is established by introducing the hyperbolic tangent function, and the steady temperature field is deduced by solving the one-dimensional steady-state heat transfer equation. The nonlinear governing equations are derived by application of Hamilton principle and solved by finite difference method, Newmark method and Newton-Raphson method. In numerical results, FML beams constrained by different boundary conditions are selected to reveal the dynamic properties of FML beams. The effects of some parameters are discussed in detail, and some meaningful conclusions are concluded.

Steady-State Three - Dimensional Numerical Simulation of Heat Transfer for Thermal Bridges Assessment

Abstract This paper presents a study on using the steady-state three-dimensional heat transfer software HEAT3 for evaluating the heat flow of heat transfer through different elements of the building envelope in order to establish the linear thermal transmittance of the linear thermal bridge. The linear thermal transmittance is obtained according to the one-dimensional steady-state heat transfer calculation formula for the plane walls using the heat flow values obtained through the method specified above. The results presented in this paper are part of a wider study on evaluating the heat transfer through building’s envelope elements by evaluating as accurate as possible the thermal bridges effect of the most common building structures. As a case study, it was considered the steady-state heat transfer through an opaque outer wall of a building considering the thermal bridges for the following elements: outer walls intersection, inner and outer wall intersection and outer wall with intermediate floor intersection.

A Ubiquitiformal One-Dimensional Steady-State Conduction Model for a Cellular Material Rod

A ubiquitiformal model for the one-dimensional steady-state heat transfer of a cellular material rod is developed in this paper, and the explicit analytical expressions for both the temperature distribution and the equivalent thermal conductivity are obtained. The calculated results for two kinds of dry soil are found to be in good agreement with previous experimental data. Moreover, it is demonstrated that the ubiquitiformal model is more reasonable for describing such a cellular material than the fractal one, and hence a ubiquitiformal rather than a fractal model should be considered in practical applications whenever the integral dimensional measure of a real physical object must be taken into account.

Electrical conductivity and Joule heating of polyacrylonitrile/carbon nanotube composite fibers

Carbon nanotube (CNT) can exhibit electrical conductivity and introduce electric current into polymer. Using dry-jet-wet spin technology, polyacrylonitrile (PAN)/CNT composite fibers with 15 wt% and 20 wt% of CNT content were fabricated. The electrical conductivity of PAN/CNT fibers was enhanced by the annealing process at different temperatures and changed with time. These fibers could also respond to stretching, and the electrical conductivity decreased by 50% when the elongation reached 3%. In addition, electrical current can induce Joule heating effect and thermally transform PAN/CNT composite fibers. With the application of various electrical currents up to 7 mA at a fixed length, conductivity was enhanced from around 25 S/m to higher than 800 S/m, and composite fibers were stabilized in air. The temperature of composite fibers can increase from room temperature to several hundreds of degree Celsius measured by an infra-red (IR) microscope. Joule heating effect can also be estimated according to one-dimensional steady-state heat transfer equation, which reveals the temperature can be high enough to stabilize or carbonize fibers. As a result, this research provides a new idea of heating fabrics for thermal regulation, and a new approach for stabilizing and carbonizing PAN-based carbon fibers.

Some Exact Solutions of Nonlinear Fin Problem for Steady Heat Transfer in Longitudinal Fin with Different Profiles

One-dimensional steady-state heat transfer in fins of different profiles is studied. The problem considered satisfies the Dirichlet boundary conditions at one end and the Neumann boundary conditions at the other. The thermal conductivity and heat coefficients are assumed to be temperature dependent, which makes the resulting differential equation highly nonlinear. Classical Lie point symmetry methods are employed, and some reductions are performed. Some invariant solutions are constructed. The effects of thermogeometric fin parameter, the exponent on temperature, and the fin efficiency are studied.

Thermal performance of mechanical face seal with built-in heat pipe

Performance of a prototype mechanical face seal with built-in heat pipe is experimentally evaluated. The results demonstrate the feasibility of using phase change to remove frictional heating and thus reduce interfacial temperature. In this design, the heat pipe is integrated into the seal mating ring and there is no need to modify the gland design or the flush arrangement. The experimental results show that by means of phase change, this design is capable of significantly reducing the temperature at the seal rings’ interface. To gain insight into the heat transfer enhancement of the heat pipe mating ring, a one-dimensional steady-state heat transfer analysis is applied to predict the ring wall temperature distribution and to estimate the saturated vapor temperature. The effective thermal conductivity of heat pipe mating ring is estimated. These results of prediction are in good agreement with experimental measurements.

A One-Dimensional Heat Transfer Model Analysis of Heat Sinks

A one-dimensional steady-state heat transfer model of heat sinks is proposed to determine the heat sink size needed for a given heat source. Both the temperature distribution and the maximum heat source temperature solution are presented analytically. The results are in closed form and can be conveniently used for determining the heat sink size. The two most important dimensionless parameters that describe the geometry and heat transfer characteristics of the heat sinks are defined and their influences on the maximum temperature of heat sinks are analyzed. The results show that the maximum heat source temperature decreases with the heat sink size. It is also shown that if the heat sink size is large enough then the effectiveness in reducing the maximum heat source temperature by increasing the heat sink size is significantly decreased.

A study about one-dimensional steady state heat transfer in cylindrical and spherical coordinates

In this article were developed one-dimensional steady state heat transfer equations in cylindrical and spherical coordinates, neglecting or not the viscous dissipation. We used second order approximations for the development of a computational code. Some applications were made and errors were analyzed.

Research on Simulation of Operation of DSG Collectors Based on Analysis of Scientific Materials

In this paper, a direct steam generation (DSG) collector is researched. To determinate the DSG collector efficiency, a simplified heat loss correlation is applied. A one-dimensional steady state heat transfer model and an energy balance equation for DSG collector are developed. A Visual basic program coupled with fluid parameters is compiled to compute fluid temperature, heat transfer coefficient and heat loss along the absorber tube by iterations for given accuracy. The variation trends of many kinds of fluid parameters along the absorber tube are revealed. The effect of length of dry steam region on collector efficiency is accounted for also.

Analysis of Ohno continuous casting process using one-dimensional steady state heat transfer model

The Ohno continuous casting process is being used regularly in the unidirectional crystallisation of high purity copper and silver wires for electronics applications. Many experimental investigations have been carried out on both fundamental and practical aspects of the process. This paper deals with the feasibility of a one-dimensional heat transfer approach for the analysis of the effect of the crucial processing parameters. The results on the effects of varying the parameters based on the calculation of the temperature profiles along the axis of the cast rod were in accord with the experimental results in the literature, indicating that the one-dimensional approach can be used as an analytical tool for the process.