Heat Loss Calculation Research Articles

A simple methodology to predict heating load at an early design stage of dwellings

This paper compares several different simplified methodologies for building energy performance assessment during winter time selected based on its large application and/or its user friendly characteristics. Hourly values for energy demand are calculated by a detailed comparison tool based on hourly weather data. A simplified building procedure spreadsheet to evaluate energy demand is also presented. It gives reliable results, needs only a little input data to describe the building design and low time consumption. The spreadsheet is therefore useful for preliminary design tasks in the early design stages where rough estimates of the building design and preliminary energy use are needed for primary decision support. The method is based on a seasonal heating calculation of heat losses and usable heat gains for the building, where the heat-accumulating capacity of the building is considered. The seasonal mean values of the solar radiation and degree days are applied. This paper describes the applied calculation technique and the assumptions made to carry out heating calculation.

Estimation of characteristic temperature ratios for panel radiator and high temperature radiant strip systems to calculate heat loss within a room space

When a building is heated to a steady internal temperature, equilibrium is established in which the heat power into the building equals the rate at which heat is lost from the building. A good approximation of heat losses can be determined using the conventional generic equations which give a relatively accurate value of the heat loss; however these equations can be inaccurate, especially in applications where radiative heating is used. In this article simple predictive tools are developed to estimate the characteristic temperature ratios for both panel radiator and high temperature radiant strip systems. The calculated results can be used in follow up calculations for a model, which fully takes into account the radiation heat transfer occurring within a room space.The results of the proposed method are found to be in excellent agreement with reported data in the literature with average absolute deviation being around 0.2%.The predictive tool is simple and straightforward and it can be readily implemented in a standard spreadsheet program. The prime application of the method is as a quick-and-easy evaluation tool in conceptual development and scoping studies where a panel radiator system and a high temperature radiant strip system are being considered. The method may also serve as a benchmark in numerical and rigorous simulation studies.

Importance of heat transfer in an anaerobic digestion plant in a continental climate context

Investigation on the sensivity to temperature variations has been achieved on a full-scale experimental dairy wastewater treatment plant including an unheated but insulated upflow anaerobic sludge blanket. A simple steady-state heat transfer model based on energy balance has been designed to forecast the biogas production depending on ambient air and dairy wastewater temperatures variations. Energy balance has been described for any part of the digestion plant. Calculated heat losses were in the same range than observed losses with an uncertainty of about 10%. From the equalization tank to the digester the average heat loss under cold period was close to 10°C due to convection and conduction. Mesophilic conditions are not respected for couples of ambient air and wastewater temperatures ranging respectively from 8–35 to 35–29°C. Technical solutions are suggested to increase the biogas production.

Effect of massive outer leaf of an insulated cavity brick wall on heat loss

The availability of coherent long-term measured data on climatic variables and building parameters forms the basis for predicting, analyzing, and simulating the heating or cooling energy demand on buildings. This article analyzes measured 4-year data considering the test building with an insulated cavity brick wall with a massive outer brick leaf. The results show that the solar radiation and the thermal inertia of massive outer leaf of a wall have a significant effect on the heat loss and energy consumption of the buildings throughout Finland and Scandinavia. Based on the average outdoor air temperatures, the nominal calculated heat losses could be overestimated. For more accurate heat losses, the outdoor surface temperature should be applied as a boundary condition. The measured results were verified with finite element method.

Control and amount of heat dissipation through thermal windows in harbor seals (Phoca vitulina)

Pinnipeds have to cope with the thermoregulatory demands of their amphibious lifestyle. As they are effectively insulated against heat loss in water by their blubber, they have to bypass the blubber for heat dissipation while staying ashore. In previous studies thermal windows on the body of captive phocid seals have been described as areas of heat dissipation in air. In this study we used infrared thermography (IRT) to examine thermal windows in seals hauling out as well as in training situations, where the first refers to a voluntary and the latter to an induced stay on shore. Furthermore we provide an IRT-based estimate of heat loss through thermal windows in pinnipeds. Hauling out seals developed thermal windows within a few minutes irrespective of environmental conditions. By contrast, seals staying on shore on a trainer's command did not develop thermal windows at all. The calculation of heat loss through thermal windows resulted in considerable values in air, but above all in water, which is energetically disadvantageous as it takes up to four minutes to close thermal windows in water.

Ground contact heat losses: Simplified calculation method for residential buildings

Heat loss through building elements in contact with the ground plays an important role in a building's thermal behaviour, therefore its estimation and management is relevant when assessing a building's energy performance. The EN ISO 13370 standard provides a method for calculating heat loss through the ground that takes into account steady state heat loss as well as heat loss due to temperature variations throughout the year (on a monthly or seasonal basis). It is based on calculating thermal transmittance for floors and walls in contact with the ground and differs greatly from the method established in the Portuguese building regulation codes. The EN ISO 13370 method requires a large input of data. This paper presents an alternative simplified version of the method that is more suitable for general building energy performance calculation procedures since it requires fewer calculation parameters and steps. The proposed method is mainly conservative and overestimates slightly heat transfer via the ground when compared to the EN ISO 13370 standard method.

Linear non-adiabatic flow of an incompressible fluid in a porous layer – Review, adaptation and analysis of the available temperature models and solutions

This article will concentrate on the problem of 2D heat losses from a reservoir experiencing linear flow of an incompressible fluid with a uniform heat generation in the reservoir. This problem can be instantly attributed to some specific, industrially relevant cases, e.g. estimation of the transient temperature distribution in a hydraulic fracture. However, its main value is that it is an integral part of the full, transient temperature solution for the flow of low compressible fluids (i.e. liquids and, sometimes, gases) into horizontal wells. The full solution is essential for temperature transient analysis in smart wells – a monitoring approach of great potential, but in early development stage.This article will first discuss the problem of the temperature transient analysis, the flow conditions and the assumptions required to sufficiently simplify the thermal model so that existing solutions can be applied, and their applicability confirmed. Secondly, we will discuss some closely related problems whose solutions are already available, along with the modifications required to apply them to our case. The article continues with a numerical study that was carried out to check the applicability of the existing (modified) solutions. We will either include, or discuss, all the relevant physical phenomena affecting the flowing fluid (Joule–Thomson effect, transient thermal expansion, friction losses, and multi-dimensional heat losses). Finally, a novel approach for the calculation of semi-steady state heat losses from a reservoir to the surrounding formation will be presented. It is based on the solution to the “hot fluid injection” problem with appropriate corrections.

냉장고 역열손실 방법의 수치해석적 분석에 관한 연구

The present study has been carried out to predict the heat transfer characteristics of reverse heat loss method for a residential refrigerator by using numerical analysis and corresponding experiment. From the measured values of temperature and heat input, one can conclude that, the temperature inside the refrigerator has a nearly linear relationship with heat input. The effect of gasket heat loss was examined with the change of thermal conductivity of gasket region. The appropriate thermal conductivity of gasket region was acquired from the comparison of heat losses with the experimental result and numerical analysis. The result of calculated heat losses had accuracy within 1.8% error with the experimental result. With the selected thermal conductivity of gasket region, the effectiveness of reverse heat loss method was examined with the change of thermal conductivity of vacuum insulation panel.

Numerical study of conduction and convection heat losses from a half-insulated air-filled annulus of the receiver of a parabolic trough collector

Abstract Grid-quality parabolic trough collectors utilize expensive receivers that maintain vacuum in their annuli to reduce convection losses. On the other hand, receivers with air-filled annuli, currently used mainly for process heat applications, are significantly less expensive, but their thermal performance is inferior to evacuated receivers. A promising technique that can bridge the cost and performance gap between the two types of receivers is introduced in this work. A heat-resistant thermal insulation material is fitted into the portion of the receiver annulus that does not receive concentrated sunlight. The presence of this insulation material is expected to reduce not only convection heat losses, but also radiation losses. This study focuses on the calculation of conduction and convection heat losses from the proposed receiver using numerical modeling. The performance of the proposed concept is compared to that of a conventional receiver with an air-filled annulus. The results have shown that the combined conduction and convection heat loss from the proposed receiver can be smaller than that from a receiver with an air-filled annulus by as much as 25% when fiberglass insulation is used. However, the fact that the thermal conductivity of the insulating material increases with temperature reduces the benefit of the proposed concept at high temperatures. As a result, the proposed receiver is expected to be suitable as a replacement for receivers with air-filled annuli or as an economical alternative to evacuated receivers that are used at the lower temperature end of utility-scale solar power plants.

Method for optimal design of pipes for low-energy district heating, with focus on heat losses

The synergy between highly energy-efficient buildings and low-energy district heating (DH) systems is a promising concept for the optimal integration of energy-saving policies and energy supply systems based on renewable energy (RE). Network transmission and distribution heat loss is one of the key factors in the optimal design of low-energy DH systems. Various pipe configurations are considered in this paper: flexible pre-insulated twin pipes with symmetrical or asymmetrical insulation, double pipes, and triple pipes. These technologies represent potential energy-efficient and cost-effective solutions for DH networks in low-heat density areas. We start with a review of theories and methods for steady-state heat loss calculation. Next, the article shows how detailed calculations with 2D-modeling of pipes can be carried out by means of computer software based on the finite element method (FEM). The model was validated by comparison with experimental measurements, analytical formulas, and data from the literature. We took into account the influence of the temperature-dependent conductivity coefficient of polyurethane insulation foam, which enabled us to achieve a high degree of accuracy. We also showed the influence of the soil temperature throughout the year. Finally, the article describes proposals for the optimal design of pipes for low-energy applications and presents methods for decreasing heat losses.

Heat-loss calculation in ladle treatment of steel

A mathematical model permits calculation of the heat losses and temperature variation of liquid steel. The rates of variation in the heat losses and the integral mean temperature of the liquid steel are physically interpreted. A semiempirical formula that performs well in practice is used for the emissivity of slagmetal melt during discharge from a converter. Good agreement is found between the calculated and actual temperature values of the steel in a casting ladle for a continuous-casting machine.

Thermodynamic analysis of a building using exergy analysis method

This study deals with exergetic assessment of an educational building heated by a conventional boiler in a heating center. The heating system is examined from the generation stage to the envelope of the building. In general the heat loss calculations are made using both energy and exergy analysis methods. The energy and exergy flows between the stages are obtained using a pre-design tool for an optimized building design. Energy and exergy losses are obtained to evaluate the performance of the system. A conventional boiler in the heating center and a fan coil unit in a room are considered in the analysis. Total exergy input rate is calculated to be 694.5 kW, while the largest exergy loss rate is obtained to be 333 kW. Exergetic efficiencies of the conventional boiler and the fan coil unit are also found to be 13.4% and 37.6%, respectively.

Heat insulation of high-temperature heating units for ceramic production

Heat losses are studied for a tunnel furnace used for firing porcelain and refractory materials. Calculations of the heat losses through the arch of the furnace are performed using diatomaceous crumb and granulated foam glass ceramic as heat-insulating fill. Cost-effectiveness calculations show that there is an advantage to using granulated foam glass ceramic.

Calculation and analysis of dissipation heat loss in large-scale circulating fluidized bed boilers

Abstract In the present work, experimental studies of dissipation heat loss were carried out on two types of 300 MWe circulating fluidized bed (CFB) boilers. Results indicated that there was great difference of dissipation heat loss between the two types of CFB boilers. Under the full work load, one boiler’s dissipation heat loss was more than twice as that of another. The difference of dissipation heat loss between the boilers was mainly from differences of heat dissipating capacities in cyclones. Compared with steam cooled cyclone, there was much more heat dissipating from hot cyclone to the surroundings for the hot cyclone has a relatively higher surface temperature and larger surface area. Since the existing empirical curves cannot fully reflect the difference, it is inclined to calculate the heat loss according to test codes issued by ASME or EPRI. In order to reduce the large amount of measurements, a simplified suggestion was introduced and results showed the matching between the simple method and measurements was good.

Calculation model of on-way parameters and heating radius in a superheated steam injection wellbore

Abstract As superheated steam is a single-phase gas, it does not fit theories of ordinary steam heat loss calculation models based on two-phase flow. By using the PVT data of superheated steam, this paper builds a calculation model of on-way parameters in the superheated steam injection wellbore. The superheated steam heating area and heating radius formulae are presented. The calculated results for on-the-way change of steams in Well X16 of the Kenneyak oilfield fit well with the field test results. The analysis shows that the temperature of superheated steam varies greatly with heat transfer, the pressure varies greater than for ordinary steam, the steam quality is high when reaching the bottom hole, the steam enthalpy is much higher than for ordinary steam, and the heating radius is wider.

MEASUREMENTS OF HEAT LOSSEST DURING SOLIDIFICATION OF LIGHT MEALS

This paper describes the application of a new in-cavity thermal measurement method to determine the heat flux and calculate heat losses during high pressure die casting of aluminium A380 alloy and the magnesium alloy AZ91-D. Thermal management of the die is a critical concern in high pressure die casting and the development of microstructures after solidification. Detailed measurements were performed using infra-red probes linked to pyrometric chains and thermocouple arrays that accurately determine both casting and die surface temperatures enabling the determination of heat flux densities and interfacial heat transfer coefficients and the rapid evolution of these values with time during high pressure die casting of these alloys. The energy losses during the spray cycle can then be determined by integrating the heat flux curves for the duration of the spray application. The significance of the findings presented in this investigation arise from the uniqueness of the measurement methods applied to the determination of heat flux during the high pressure die casting of both magnesium and aluminium alloys. In particular the detailed knowledge of the thermal characteristics occurring at the cavity fill stages of the die casting process achieved through the selection of an array of fine rapid-response thermocouples integrated in one sensor along with the light pipe/pyrometric chain have enabled the accurate measurement of both the die and metal surface temperatures through the entire die casting cycle enabling the calculation of heat losses during solidification and processing.

Thermal analysis of an historical Turkish bath by quantitative IR thermography

The study is focused on the use quantitative IR thermography (QIRT) for the examination of thermal performance of an historical Turkish bath (hamam). A simple heat transfer model was applied to achieve reference surface temperatures during the IRT surveys. The reference temperatures calculated and the real surface temperatures measured have been compared each other to better understand the thermal performance of historical structure in a non destructive way. Another issue was the failures evaluation in relation to the recent restoring interventions. The study was supported by microclimatic monitoring of indoor and outdoor conditions. The thermophysical properties of the historic materials were determined by laboratory analysis and the data were used for the heat loss calculations

Numerical simulation of the thermal state of a flooded pipeline taking into account unsteadiness of the process of heat insulation saturation with moisture

The calculation of pipeline heat losses during operation under conditions of pipeline channel flooding is considered. A mathematical model is suggested allowing one to analyze thoroughly and in time the process of saturating heat insulation with moisture and the growth of heat losses associated with this process.

Spherical harmonic analysis of earth’s conductive heat flow

A reappraisal of the international heat flow database has been carried out and the corrected data set was employed in spherical harmonic analysis of the conductive component of global heat flow. Procedures used prior to harmonic analysis include analysis of the heat flow data and determination of representative mean values for a set of discretized area elements of the surface of the earth. Estimated heat flow values were assigned to area elements for which experimental data are not available. However, no corrections were made to account for the hypothetical effects of regional-scale convection heat transfer in areas of oceanic crust. New sets of coefficients for 12° spherical harmonic expansion were calculated on the basis of the revised and homogenized data set. Maps derived on the basis of these coefficients reveal several new features in the global heat flow distribution. The magnitudes of heat flow anomalies of the ocean ridge segments are found to have mean values of less than 150 mW/m2. Also, the mean global heat flow values for the raw and binned data are found to fall in the range of 56–67 mW/m2, down by nearly 25% compared to the previous estimate of 1993, but similar to earlier assessments based on raw data alone. To improve the spatial resolution of the heat flow anomalies, the spherical harmonic expansions have been extended to higher degrees. Maps derived using coefficients for 36° harmonic expansion have allowed identification of new features in regional heat flow fields of several oceanic and continental segments. For example, lateral extensions of heat flow anomalies of active spreading centers have been outlined with better resolution than was possible in earlier studies. Also, the characteristics of heat flow variations in oceanic crust away from ridge systems are found to be typical of conductive cooling of the lithosphere, there being little need to invoke the hypothesis of unconfined hydrothermal circulation on regional scales. Calculations of global conductive heat loss, compatible with the observational data set, are found to fall in the range of 29–34 TW, nearly 25% less than the 1993 estimate, which rely on one-dimensional conductive cooling models.

Evidence for heat losses via party wall cavities in masonry construction

This paper presents empirical evidence and analysis that supports the existence of a significant heat loss mechanism resulting from air movement through cavities in party walls in masonry construction. A range of heat loss experiments were undertaken as part of the Stamford Brook housing field trial in Altrincham in the United Kingdom. Co-heating tests showed a large discrepancy between the predicted and measured whole house heat loss coefficients. Analysis of the co-heating results, along with internal temperature data, thermal imaging and a theoretical analysis indicated that the most likely explanation for the discrepancy was bypassing of the thermal insulation via the uninsulated party wall cavities. The data show that such a bypass mechanism is potentially the largest single contributor to heat loss in terraced dwellings built to the 2006 revision of the Building Regulations. A comparable convective heat bypass associated with masonry party walls was identified in the late 1970s during the course of the Twin Rivers Project in the United States, albeit in a somewhat different construction from that used at Stamford Brook. A similar effect was also reported in the United Kingdom in the mid 1990s. However, it appears that no action was taken at that time either to confirm the results, to develop any technical solutions, or to amend standards for calculating heat losses from buildings. Current conventions for heat loss calculations in the United Kingdom do not take account of heat losses associated with party walls and it is suggested by the authors that such conventions may need to be updated to take account of the effect described in this paper. In the final part of the paper, the authors propose straightforward solutions to prevent bypassing of roof insulation via party walls by for example filling the cavity of the party wall with mineral fibre insulation, or by inserting a cavity closer across the cavity in the plane of the roof insulation. Practical application: The heat bypass mechanism described in this paper is believed by the authors to contribute to a significant proportion of heat loss from buildings in the UK constructed with clear cavities such as those found in separating walls between cavity masonry dwellings. It is proposed that relatively simple design changes could be undertaken to eliminate such heat loss pathways from new buildings. In addition, simple and cost effective measures are envisaged that could be used to minimise or eliminate the bypass from existing buildings. Such an approach could give rise to a significant reduction in carbon emissions from UK housing. a The Department for Communities and Local Government, previously the Office of the Deputy Prime Minister, ODPM. References produced before the change of name are listed under ODPM. b Difficulties in the recruitment of households have delayed the long term monitoring programme to 2007 but, fortuitously, this has provided the capacity for a more detailed investigation of the party wall heat loss issues discussed in this paper with further co-heating tests (incorporating a more detailed measurements) planned for the winter of 2006/07. c A co-heating test involves electrically heating the inside of a house to a constant temperature over a period of several weeks. Correlation of the measured electrical heat input with external temperature and solar insolation then allows an estimation of the total dwelling heat loss coefficient. d House A is an end-of-terrace house with one adjacent house. House E is a mid-terrace house with two adjacent houses, D and F. e In the UK, the regulations consist of a broadly framed, performance based, legal requirement supported by detailed technical guidance on compliance. Such guidance is provided by a system of approved documents issued by the Secretary of State. The current methodology for dwelling heat loss calculations is contained in the Standard Assessment Procedure 200512 which is invoked by regulation 17A and Approved Document L1A.2 f The Building Regulations do limit the leakage of air from within each dwelling into the cavity through an overall limit on dwelling permeability. g The higher-than-normal inside-outside temperature difference during the co-heating tests implies that background ventilation rates and ventilation heat loss coefficients during these tests are likely to have exceeded those in the table. Calculations based on a semi-analytical model of air flow14 suggest that the increase is of the order of 3 WK—1 (10%) for the two-storey house A and 15 WK—1 (27%) for the three-storey house E. h Note that the correction is only used to improve the graphical presentation of the data. The heat loss coefficient is calculated directly from multiple regression of heating power against ΔT and S.