Prediction Of Heat Loss Research Articles

An optimal operational scheduling model for energy-efficient building with dynamic heat loss prediction

Building energy systems with circulation loops have high circulation heat loss, resulting in low energy utilization efficiency. It requires energy-saving operation strategies to eliminate unnecessary circulation heat loss, especially in domestic hot water (DHW) systems. The objective of this paper is to improve the energy efficiency of building energy systems and reduce operational costs. This is done by dynamically adjusting the target temperature set point. This is the first study to present a computationally inexpensive method for accurately predicting the temperature drop of hot water in environments with changing ambient temperatures. The outcome indicates that energy usage efficiency could be increased by approximately 16.42 %, while operational costs could be lowered by approximately 24.76 % for over 90 days in the fall. The proposed model is an implementable approach for predicting temperature drop and optimal operational scheduling as part of robust and reliable building energy management in real-world scenarios.

Convective heat loss prediction from conical cavity receiver of solar parabolic dish collector using numerical method and artificial neural network

In this work, detailed investigations of convection heat loss from conical cavity receiver of solar parabolic dish collector using a numerical method and artificial neural network have been performed. The convective heat loss from the cavity receiver is primarily influenced by geometrical parameters, receiver orientation, and wind characteristics. The heat loss estimation is carried out by considering wind speed (V = 0–10 m/s), wind direction ( = 90 and −90), receiver tilt ( = 0–90), diameter to height ratio (d/h = 0.5–1.5), and surface temperature (T s = 500–800 K). The utmost heat loss occurs at a tilt of 60 for d/h < 1 and 75 for d/h 1 in head-on high wind speed, while in back-on high wind speed, it occurs at a tilt of 30 for all d/h values. The heat loss is lowest at 90° for V > 4 m/s. The d/h value of 0.5 performs well compared to other values. Further, the correlation for the Nusselt number has been proposed for the conical cavity receiver.

Numerical study of chemical kinetics and radiation heat transfer characteristics on the temperature distribution in the oxy-fuel combustion

In this study, The IFRF methane-oxygen combustion furnace is used to investigate the effect of the radiation model, the method of evaluated absorption and emission coefficients and the different chemical mechanisms. The simulations are performed with OpenFOAM open source software by using of PaSR (partially stirred reactor) combustion model. The numerical investigations are carried out without radiative heat transfer and with the modeling of the radiation source term using the P1 (spherical harmonic radiation model) and DO (discrete ordinate) models. To evaluate the absorption and emission coefficients used from the constant coefficients, the grey mean gases model in terms of temperature polynomial, the WSGGM (weighted sum of grey gases model) and refined WSGGM models. The investigation of the global mechanism effect on the temperature distribution in the oxy-fuel combustion is performed by the modified 2-step Westbrook-Dryer mechanism by Yin and modified 4-step Jones-Lindstedt mechanisms by Yin and Andersen. The results indicate that the lack of consideration of radiation heat transfer in the oxy-fuel combustion leads to a large error in the prediction of the maximum and average temperature distributions inside the furnace. Also, the DO model has less error than P1 model due to more heat loss prediction by P1 model in the low optical thickness. The WSGGM model for calculating of absorption and emission coefficients provide the best result in comparison with other methods. The refined 4-step Jones-Lindstedt mechanism by Andersen has best prediction of on the basis of numerical simulations.

Numerical prediction of heat loss from a test ribbed rectangular channel using the conjugate calculations

Conjugate heat transfer of air and steam in a rectangular channel with 90° ribs along two opposite walls was investigated experimentally and numerically. The stainless steel test section was 80 mm × 40 mm × 2.5 mm and the ribs were 80 mm × 2.5 mm × 2.5 mm with 25 mm between ribs. The tests investigated the effects of coolant mass flow rate (the corresponding Reynolds numbers in the range of 10,000-50,000) on the conjugate heat transfer enhancement with the ribs. Two conjugate heat transfer calculation methods with different models were developed. For the first model (CHT-Q model) solid domain was viewed as a uniform internal heat source with the adiabatic exterior surfaces, while for the second model (CHT-T model) the outwall temperature was specified by the fitting polynomials of measured data with the zero internal heat. Comparisons between the experimental and numerical results showed that the SST k–ω turbulence model was more suitable for the conjugate heat transfer in such channels. Regardless of numerical error, an approximation of heat loss was specified by the successive trial calculations of the CHT-Q model, while a relatively accurate heat loss was evaluated by the post-processing of the CHT-T calculation. Local heat transfer coefficient can be determined accurately by the quantified heat loss of test system. The critical impact of conjugate heat transfer was demonstrated. Furthermore, the steam coolant compared to air exhibited a higher heat transfer performance by 12–25% for both the ribbed and smooth walls at the same Reynolds number.

Heat loss prediction of a confined premixed jet flame using a conjugate heat transfer approach

The presented work addresses the investigation of the heat loss of a confined turbulent jet flame in a lab-scale combustor using a conjugate-heat transfer approach and large-eddy simulation. The analysis includes the assessment of the principal mechanisms of heat transfer in this combustion chamber: radiation, convection and conduction of heat over walls. A staggered approach is used to couple the reactive flow field to the heat conduction through the solid and both domains are solved using two implementations of the same code. Numerical results are compared against experimental data and an assessment of thermal boundary conditions to improve the prediction of the reactive flow field is given.

Mathematical Model Prediction of Heat Losses from a Pilot Sirosmelt Furnace

Mathematical Model Prediction of Heat Losses from a Pilot Sirosmelt Furnace

Extended Heat Loss and Temperature Analysis of Three Linear Fresnel Receiver Designs

Heat loss prediction models for parabolic trough receivers do not consider the thermal effect of a secondary mirror. As an extension a Thermal Resistance Model (TRM) has been developed at Fraunhofer ISE for the prediction of the heat loss of three different Linear Fresnel Collector (LFC) receiver configurations. In previous investigations we have found the energy balance of a LFC receiver to be strongly influenced by the amount of solar radiation absorbed by the secondary mirror. This absorption provokes an increase of temperature of the secondary mirror and hence a decrease in the total amount of heat loss of a LFC. The size of this effect depends on the receiver geometry and diverse ambient parameters. Investigated parameters are wind velocity, ambient temperature and Direct Normal Irradiance (DNI). This dependency and its effect on heat loss and secondary mirror temperatures are analyzed for three different LFC receiver configurations. As the radiation absorbed by the secondary mirror is affected by the aperture area of the LFC, studies are performed for small-scale and for large-scale collectors.

Application of Software for the Prediction of Heat Loss in Outdoor Condition during Physical Activity in Nigeria

Application of Software for the Prediction of Heat Loss in Outdoor Condition during Physical Activity in Nigeria

Experimental study of heat transfer characteristics for a refrigerator by using reverse heat loss method

The present study has been carried out to predict the heat transfer characteristics of a residential refrigerator through insulation wall by using reverse heat loss method. The temperature time history characteristics were measured to achieve the steady state condition. In this experiment the steady state condition was reached at about 20 h of heating. The temperature and heat inputs were then averaged with one hour data and considered as the steady state temperature and heat input. From the measured values of temperature and heat input, one can conclude that, the temperature differences between the inside and outside of a refrigerator has a nearly linear relationship with heat input. The overall heat transfer coefficients have been derived by introducing the optimal heat loss function to analyze the heat loss characteristics. The accuracy of heat loss prediction has been checked with various experimental data and the normalized errors of the obtained result are found to be within 2.5%.

Convection heat loss from cavity receiver in parabolic dish solar thermal power system: A review

The convection heat loss from cavity receiver in parabolic dish solar thermal power system can significantly reduce the efficiency and consequently the cost effectiveness of the system. It is important to assess this heat loss and subsequently improve the thermal performance of the receiver. This paper aims to present a comprehensive review and systematic summarization of the state of the art in the research and progress in this area. The efforts include the convection heat loss mechanism, experimental and numerical investigations on the cavity receivers with varied shapes that have been considered up to date, and the Nusselt number correlations developed for convection heat loss prediction as well as the wind effect. One of the most important features of this paper is that it has covered numerous cavity literatures encountered in various other engineering systems, such as those in electronic cooling devices and buildings. The studies related to those applications may provide valuable information for the solar receiver design, which may otherwise be ignored by a solar system designer. Finally, future development directions and the issues that need to be further investigated are also suggested. It is believed that this comprehensive review will be beneficial to the design, simulation, performance assessment and applications of the solar parabolic dish cavity receivers.

Thermomechanical Simulation of Infrared Heating Diaphragm Forming Process for Thermoplastic Parts

An innovative methodology for the thermomechanical simulation of the infrared heating diaphragm forming (DF) process is proposed. In the first section of the paper, the heat transfer mechanisms between the infrared (IR) heating lamps and the thermoplastic plate are simulated, and the effect of the various preheating parameters on the heating time and temperature distribution is investigated. In the second section, the mechanical deformation of the thermoplastic component is simulated to enable prediction of heat losses due to the plate contact with the mold. Based on the developed simulation methodology, the main process parameters — e.g., the number, location, and power of IR lamps for optimal preheating; the heat losses during plate deformation; and the minimum required mold temperature throughout the forming phase — are derived for five different thicknesses. The optimization results show that the forming parameters considered influence the heating of the plate in a complex and interactive way; in addition, it is found that with increasing plate thickness, the heating time required to reach the desired temperature also increases.

Prediction of heat losses by conduction and radiation from total heat loss data for degraded evacuated collectors

Prediction of heat losses by conduction and radiation from total heat loss data for degraded evacuated collectors

Heat Transfer Models for a Subsurface, Water Pipe, Soil‐Warming System

AbstractMathematical models are developed for the prediction of heat losses from subsurface pipes carrying hot water. The method of images is used to calculate the heat loss from a hot water pipe buried at a given depth below the surface of a homogeneous soil with a constant soil surface temperature. The heat loss is described as a function of the difference between the temperature of the water and the temperature of the soil surface. The energy balance is used to determine the longitudinal temperature distribution of the water. The method is extended to describe the heat loss and the longitudinal temperature distribution for a system of equally spaced, parallel, subsurface pipes with water flowing in the same direction in neighboring pipes. Finally, the method is extended to calculate the heat loss and the longitudinal temperature distribution for a system of equally spaced, parallel, subsurface pipes with water flowing in opposite directions in neighboring pipes. Soil temperature profiles around the buried pipes are presented. The models are used to calculate the land area which can be heated with an underground piping system carrying the cooling water from the condensers of a 1000‐megawatt nuclear‐powered steam generation electric power plant.

Prediction of heat losses from cattle exposed to cold outdoor environments.

Prediction of heat losses from cattle exposed to cold outdoor environments.

Factors affecting blue goose nesting success

Blue geese at McConnell River, N.W.T., lost 20% of eggs, mostly late in incubation. Parasitic jaegers and herring gulls were attracted to the colony and were efficient at finding eggs although geese defended their nests strongly. Since egg loss could only occur in the absence of both geese, jaegers, and gulls acted as scavengers rather than predators. Factors causing desertion were the true causes of egg loss. These may have been inexperience of younger geese, or starvation during incubation.During nesting, geese had very little to eat and lost about 25% of spring weight. While the birds were fasting, weight loss is a function of heat loss, in turn controlled by weather conditions. The relationship between heat loss and several weather parameters was determined by means of a water-heated model goose in a simulated environment. This relationship allowed prediction of heat loss, and hence weight loss, from air temperature, wind speed, incident radiation, and goose surface temperature.Severe weather could result in considerable weight loss and it is suggested that this impaired the goose's ability to incubate steadily. Extreme weight loss could result in death, and many nesting geese were found apparently starved during the hatch.

Casing Temperature Studies in Steam Injection Wells

Abstract The key to realistic casing stress analysis in thermal recovery installations is accurate knowledge of the temperatures involved. Much information leading to prediction of heat losses from tubing string to wellbore has been published. This same information permits calculation of casing temperature under certain conditions. This paper reviews the basis for most of the published work, the line sources solution to the diffusivity equation and examines some of its application criteria in the light of unsteady-state conditions. An alternate finite differences method is presented for correlation, and experimental data pertaining to the heat transfer mechanism in the annulus is reported. In the light of the information presented in the paper, it appears that the assumption of a line source for the tubing-wellbore system is valid even for reasonably short periods of heat flow, such as "steam soak" operations. The empirically modified equation presented earlier matches computer derived results of the finite differences approach for periods as short as 50 hours. Previously predicted casing temperatures and the associated stress levels are thus verified based on these correlative computations and the reported experimental information. Fall-out from the computer output resulting in some studies of the influence of insulating cement properties on casing temperature, and experimentally studied effects of nitrogen placed in the annulus at various pressures, are described. Introduction Generally speaking, predictions of average casing temperatures have been based on an idealized model involving a centralized tubing string at uniform constant temperature radiating energy towards the casing under steady-state conditions. Heat is transferred away from the casing to the formation by unsteady-state conduction across thermal barriers consisting of cement and the mud sheath., Heat balances written on the casing permit prediction of instantaneous casing temperatures. During early periods of injection, casing temperature varies appreciably as a function of time; however, for long injection times this variation decays as heat flow from the wellbore to the formation stabilizes, and it becomes virtually negligible as conditions surrounding the wellbore become quasi-steady-state (Fig. 1). Carslaw and Jaeger describe a solution to the diffusivity equation for a line source (Fig. 2). A constant supply of heat is introduced into the medium from the line placed into the origin of the x-y coordinate system and parallel to the z-axis. Heat spreads outward in the infinite cylindrical solid and the temperature increase on a line going through point (x, y) parallel to the z-axis at a distance r can be predicted by: .....(1) JPT P. 1157ˆ