Decreased Heat Loss Research Articles

Economic and Environmental Optimization of an Airport Terminal Building’s Wall and Roof Insulation

HVAC systems use the largest share of energy consumption in airport terminal buildings. Thus, the efficiency of the HVAC system and the performance of the building envelope have great importance in reducing the energy used for heating and cooling purposes. In this study, the application of thermal insulation on the walls and roof of the Hasan Polatkan Airport terminal building was investigated from energy, environment and cost aspects. This study determined the optimum insulation thickness and assessed its effects on environmental performance based on energy flows. Environmental payback periods were calculated depending on the optimum insulation thickness. The life cycle assessment (LCA) method was used to assess whether the decrease in energy consumption after applying the insulation balanced the environmental effects during the period between the production and application of the thermal insulation material. The global warming potential (GWP) based on IPCC100, and the effects on human health (HH), the ecosystem and natural resources were evaluated according to the ReCiPe method. LCA results were obtained by processing data taken from ecoinvent 3 database present in the Sima Pro 8.3.0.0 software. Applying thermal insulation on the walls and roof of the terminal building was found to decrease heat loss by 48% and 56%, respectively. In addition, the analyses showed that the environmental payback periods for the thermal insulation were shorter than the economic payback periods.

Effect of Self-Contained Breathing Apparatus (SCBA) on Heat Loss in Structural Firefighter Turnout Suits

The purpose of this research was to determine the effect of firefighter's self-contained breathing apparatus (SCBA) on heat loss through clothing ventilation openings in structural firefighter turnout suits. Passive and active ventilation openings were fabricated into structural turnout suits and tested with and without the SCBA to determine the effect on clothing ventilation. Turnout suits were evaluated under two test conditions on a sweating manikin to measure thermal and evaporative resistance. A predicted total heat loss (THL) value was calculated for each suit and compared to a control turnout without ventilation openings. A significant improvement in heat loss was measured when the SCBA harness, mask, and thermal hood were removed from the structural ensemble. Results showed the SCBA harness significantly decreased heat loss in firefighter turnouts.

Impact of a Yttria-Stabilized Zirconia Thermal Barrier Coating on HCCI Engine Combustion, Emissions, and Efficiency

In-cylinder surface temperature has significant impacts on the thermo-kinetics governing the homogeneous charge compression ignition (HCCI) process. Thermal barrier coatings (TBCs) enable selective manipulation of combustion chamber surface temperature profiles throughout a fired cycle. In this way, TBCs enable a dynamic surface temperature swing, which prevents charge heating during intake while minimizing heat rejection during combustion. This preserves volumetric efficiency while fostering more complete combustion and reducing emissions. This study investigates the effect of a yttria-stabilized zirconia (YSZ) coating on low temperature combustion (LTC), efficiency, and emissions. This is an initial step in a systematic effort to engineer coatings best suited for LTC concepts. A YSZ coating was applied to the top of the aluminum piston using a powder air plasma spray (APS) process; final thickness of the YSZ was approximately 150 μm. The coated piston was subsequently evaluated in the single-cylinder HCCI engine with exhaust re-induction. Engine tests indicated significant advancement of the autoignition point and reduced combustion durations with the YSZ coating. Hydrocarbon and carbon monoxide emissions were reduced, thereby increasing combustion efficiency. The combination of higher combustion efficiency and decreased heat loss during combustion produced tangible improvements in thermal efficiency. When the effects of combustion advance were removed, the overall improvements in emissions and efficiency were lower, but still significant. Overall, the results encourage continued efforts to devise novel coatings for LTC.

Performance analysis on a high-temperature solar evacuated receiver with an inner radiation shield

A novel solar evacuated receiver as the key part of parabolic trough collector (PTC) was designed and constructed by authors. The novel evacuated receiver (NER) with an inner radiation shield can significantly decrease heat loss at higher operating temperatures when compared with the traditional evacuated receiver (TER). A thermodynamic model relying on the spectrum parameter model of radiation heat transfer was developed to predict the performances of evacuated receivers. Also, experiments using the novel evacuated receiver and traditional evacuated receiver were conducted in the laboratory under different parametric conditions to validate results obtained for the simulation. A comparison between simulation results and experimental data demonstrated that the model was able to yield satisfactory consistencies and predictions to a reasonable accuracy (with the root mean square deviations less than 6%). Results indicated that the novel evacuated receiver has a role in decreasing the total heat loss of receiver compared with the traditional receiver when the working temperature is higher than 296 °C, the heat loss reduction percentage of the novel evacuated receiver reaches 19.1% when the operating temperature is 480 °C, and the value of this percentage would be greater at higher working temperatures.

Optimization of a Dish Stirling system working with DIR-type receiver using multi-objective techniques

Stirling engine driven by solar energy for thermal to electricity conversion is one of the most promising solution of renewable technologies to reduce the dependency from fossil fuels. Unfortunately, the lack of data about the performance and some operational parameters of this technology limited its detailed characterization and sizing. This paper presents a modeling and simulation of a Dish Stirling system working with DIR receiver (Directly Illumined Receiver), to determine its energy production and efficiency, having Itajubá a city in MG/Brazil, as case of study. Mathematical model allows determine the influence of concentrator’s parameters on overall system efficiency. Opto-geometric and transfer processes, in concentrator-receiver system are modeled in detail, and this analysis is used to develop a thermal balance of the Dish Stirling system, to determine operation parameters like: operating temperature of receiver, receiver thermal heat losses, receiver efficiency, global thermal efficiency and electrical power generated by the system. Also procedure described in this article allows to develop a sensitivity analysis for some parameters as: solar irradiation, collector diameter, wind speed and tilt angle of the cavity. Multi-objective optimization based on NSGA-II algorithm has been employed to optimize the power and the efficiency of the system, by means of integration of Dish Stirling mathematical model in Modefrontier.Numerical results show that for low wind speed the radiation heat losses have more influence over system performance, representing 96.06% of total heat losses; when wind speed is greater than 8m/s convection heat loss (45.27% of the total heat losses) becomes larger than emitted and reflected radiation. Pareto optimal front has been obtained for dual objective, and a final optimal solution has been selected using a decision-making approach by Simple Additive Weighting of decision variables (output electrical power and heat losses). Multi-objective optimization shows a way to obtain an output power of 11.1kW, with an overall efficiency of 21%, with a significant decrease in heat loss, for the weather conditions of Itajubá-MG. Model gives consistent results confirmed by experimental data used in the validation, showing also that for regions with similar environmental condition like Itajubá, it is more interesting to improve the system material, reducing radiation heat losses.

A novel method to calculate consumption of non-condensate gas during steam assistant gravity drainage in heavy oil reservoirs

The thermal recovery technology, SAGD, shows unique advantages to develop heavy oil reservoirs. A certain volume of non-condensate gas injected along with steam can effectively decrease heat loss from steam chamber to top-layer. Also, gas can dissolve in heavy oil to decrease the saturation of residual oil in the steam chamber. According to the one dimensional steady heat transfer theory, a mathematical model was introduced to optimize the thickness of gas layer during steam-gas assisted gravity drainage in heavy oil reservoir. Aiming at the dissolubility of non-condensate gas into heavy oil, a mathematical model was established to calculate injection rate of gas phase according to SAGD theory when steam and nitrogen were simultaneously injected into reservoirs. According to some geology characteristics, such as top water, large thickness, high viscosity, of an actual reservoir in China, the minimum thickness of nitrogen layer is 12.06 m, and the volume of injected nitrogen is 47.86 × 104 m3, and the injection rate of nitrogen is 5957.96 m3/d when steam and nitrogen were simultaneously injected into reservoirs after SAGD stage.

Case studies of cavity and external wall insulation retrofitted under the Irish Home Energy Saving Scheme: Technical analysis and occupant perspectives

The residential sector represents 27% of primary energy consumption in Ireland. This paper examines the case study of the Irish government’s national grant scheme to encourage energy efficiency retrofit in private housing. That is the Home Energy Saving (HES) Scheme, later rebranded the Better Energy: Homes (BEH) Scheme. The methodology involved monitoring several homes immediately before and after retrofit alongside discussions with occupants. The examination focused on specific measures commonly introduced through the HES/BEH programme − cavity and external wall insulation. It has been found that a significant decrease in heat loss through the walls was measured in all cases. Regardless, the occupant played a considerable role in the change in energy use in the buildings, and the main motivation for retrofit was found to be comfort and not energy savings or environmental concerns. As a result, the actual energy savings are notably less than the potential savings had the pre and post comfort levels remained the same.

Study of pulse drying of grain in the S-30 dryer

Innovative technologies and technical means of drying which allow to dry the grain efficiently and with minimal costs are very important for development and improvement of grain industry. These technologies include the oscillating modes, the essence of which is that the material is periodically affected by heated and unheated drying agent. These modes provide periodical grain cooling, that allows to increase drying agent temperature and decrease heat losses. However, periodical grain cooling with unheated air often lowers the effect of oscillating mode. Pulse mode, unlike the oscillating one, is characterized only by decreased liquid fuel supply in the dryer, and grain cooling on a value close to theoretical one, which allows to decrease heat losses and increase dryer efficiency. The mathematical methods of calculation of temperature and duration of impact of low-heated drying agent on the grain are suggested. To determine the temperature of low-heated drying agent and its impact duration, the heat and mass transfer equations in layer and caryopsis were composed and solved; the calculated expressions were obtained from them. During acceptance testing of the S-30 dryer, the calculated dependences for determining these parameters were checked. The wet grain was continuously sent into grain dryer, the dried and cooled grain was withdrawn at the same time. The «big fire» nozzle in firebox was periodically enabled and disabled, and the «low fire» nozzle remained in working mode, thus a pulse mode of drying was created. The maximum temperature of heated drying agent was 105 degrees С, while the temperature of low-heated drying agent was 46 degrees С. It was established that curves of changing in temperature and moisture of grain did not differ from the classic curves under oscillating drying mode. The use of pulse drying mode allows to shorten by two times the amplitude of temperature oscillations of drying agent and to reduce heat losses by 10-12%. The temperature of low-heated drying agent should not be below the maximum permissible heating temperature of grain by more than 8-10 degrees C.

On the cooling of a deep terrestrial magma ocean

Several episodes of complete melting have probably occurred during the first stages of the Earth's evolution. We have developed a numerical model to monitor the thermal and melt fraction evolutions of a cooling and crystallizing magma ocean from an initially fully molten mantle. For this purpose, we numerically solve the heat equation in 1D spherical geometry, accounting for turbulent heat transfer, and integrating recent and strong experimental constraints from mineral physics. We have explored different initial magma ocean viscosities, compositions, thermal boundary layer thicknesses and initial core temperatures.We show that the cooling of a thick terrestrial magma ocean is a fast process, with the entire mantle becoming significantly more viscous within 20 kyr. Due to the slope difference between the adiabats and the melting curves, the solidification of the molten mantle occurs from the bottom up. In the meantime, a crust forms due to the high surface radiative heat flow, the last drop of fully molten silicate is restricted to the upper mantle. Among the studied parameters, the magma ocean lifetime is primarily governed by its viscosity. Depending on the thermal boundary layer thickness at the core–mantle boundary, the thermal coupling between the core and magma ocean can either insulate the core during the magma ocean solidification and favor a hot core or drain the heat out of the core simultaneously with the cooling of the magma ocean. Reasonable thickness for the thermal boundary layer, however, suggests rapid core cooling until the core–mantle boundary temperature results in a sluggish lowermost mantle. Once the crystallization of the lowermost mantle becomes significant, the efficiency of the core heat loss decreases. Since a hotter liquidus favors crystallization at hotter temperatures, a hotter deep mantle liquidus favors heat retention within the core. In the context of an initially fully molten mantle, it is difficult to envision the formation of a basal magma ocean or to prevent a major heat depletion of the core. As a consequence, an Earth's geodynamo sustained only by core cooling during 4 Gyr seems unlikely and other sources of motion need to be invoked.

Impact of electrical heating on effective thermal Insulation of a multi-layered winter clothing system for optimal heating efficiency

Purpose This paper investigated the impact of the distance of the heating unit from the body in a multi-layered winter clothing system on effective thermal insulation and heating efficiency. Design/methodology/approach To identify changes in the thermal insulation and heating efficiency of electrical heating in different layers inside a winter clothing ensemble, a series of thermal manikin tests was conducted. A multi-layered winter ensemble with and without activation of a heating unit was tested on the thermal manikin under two different ambient temperature conditions (10°C and -5°C). Findings Results show that the effective thermal insulation of test ensembles increased by 5-7% with the activation of the heating unit compared to that without the activation. The closer the heating unit to the body, the higher the effective thermal insulation was in both ambient temperature conditions. This trend was more significant at lower ambient temperature. Research limitations/implications The results of this study indicate that providing electric heating next to the skin is the most effective in increasing effective thermal insulation and decreasing body heat loss in both ambient temperature (-5°C and 10°C). This trend was more remarkable in colder environment at -5°C of ambient temperature as evidenced by sharp decrease in heating efficiency and effective thermal insulation with an increase in distance between the manikin skin and heating unit at -5°C of ambient temperature compared to at 10°C of ambient temperature. Practical implications Based on the results, it is expected that proximity heating next to the skin, in cold environment, may reduce the weight and size of the battery for the heating unit because of the higher efficiency of electric heating and the potentially immediate perception of warmth supported by the greatest increase in effective thermal insulation, as well as the lowest heat loss that comes with activation of heating on the first layer in cold environment. Originality/value The finding of this study provides guidelines to sportswear designers, textile scientists, sports enthusiasts, and civilians who consider electric heating benefits for improved thermal comfort and safety in cold environments, especially in the areas of outdoor and winter sports and in military service. The results of this study indicate that providing electric heating next to the skin is the most effective in increasing effective thermal insulation and decreasing body heat loss in both ambient temperature (-5°C and 10°C).

Comentario sobre “Estudio aleatorizado sobre el efecto de la profilaxis antibiótica en la fiebre epidural durante el trabajo de parto”

Possibleetiologiesinclude:increasedmetabolic expenditure, decreased heat loss due to lack ofhyperventilation as a result of pain relief, thermoregulatorychanges induced by epidural analgesia, direct effects of localanesthetics on the central nervous system, paralysis of thesudoriferous glands which reduce heat loss, non-infectiousinflammatory processes and intrapartum infection, amongothers.

Human physiological responses to cold exposure: Acute responses and acclimatization to prolonged exposure.

Cold exposure in humans causes specific acute and chronic physiological responses. This paper will review both the acute and long-term physiological responses and external factors that impact these physiological responses. Acute physiological responses to cold exposure include cutaneous vasoconstriction and shivering thermogenesis which, respectively, decrease heat loss and increase metabolic heat production. Vasoconstriction is elicited through reflex and local cooling. In combination, vasoconstriction and shivering operate to maintain thermal balance when the body is losing heat. Factors (anthropometry, sex, race, fitness, thermoregulatory fatigue) that influence the acute physiological responses to cold exposure are also reviewed. The physiological responses to chronic cold exposure, also known as cold acclimation/acclimatization, are also presented. Three primary patterns of cold acclimatization have been observed, a) habituation, b) metabolic adjustment, and c) insulative adjustment. Habituation is characterized by physiological adjustments in which the response is attenuated compared to an unacclimatized state. Metabolic acclimatization is characterized by an increased thermogenesis, whereas insulative acclimatization is characterized by enhancing the mechanisms that conserve body heat. The pattern of acclimatization is dependent on changes in skin and core temperature and the exposure duration.

Study on wellbore heat loss during hot water with multiple fluids injection in offshore well

For estimating heat loss of offshore well, an analysis model of flow and heat transfer for hot water with multiple fluids injection in offshore well was established, in which multiple fluids were regarded as real gas mixture replacing the ideal gas-assumption in conventional models. Validation of the model by measured data in Bohai offshore oilfield showed that model calculation agreed with the measured data, the pressure average relative error was about 0.7%, and temperature average absolute error was about 1.4 °C. Through a simulation wellbore, the influence of some factors on heat loss of offshore well was analyzed. It was found that the heat of multiple thermal fluids lost to environment ranged from 2.3% to 9.5% under different injection parameters, and heat lost to seawater was dominant. The injection rate, injection temperature, hot water proportion and insulated tube have a great effect on heat loss of offshore well, while injection pressure, injection time and environment temperature have little effect on heat loss. An increase in injection rate, hot water proportion and depth of insulated tube, or a decrease in injection temperature and insulation thermal conductivity, leads to a decrease in heat loss, especially the heat lost to sea.

Optimum distribution of thermal insulation material for constant insulation material volume or a given investment cost

Most of the recent studies based on the alternative energy sources and efficient use of energy due to the rapidly exhausting fossil energy sources. Insulation is one of the solutions applied to decrease heat losses or gains. Present studies require tedious iterations to achieve a solution for optimum distribution of thermal insulation material for the volumes confined with environments at different temperatures such as cold storages. In this study, a general analytical solution for the optimum distribution of thermal insulation material is given for the volumes confined with environments at different temperatures for a given investment cost or constant insulation material volume. Analytical solution technique given in this study eliminates the need for tedious iterations or using a specialized computer software, and can also be combined with economic analysis models to include effects of economical parameters such as fuel price, interest rate, etc. A case study is also given for explanation and application of suggested methodology for a room confined with environments at different temperatures. It is shown that optimum distribution of insulation material easily achieved by one step analytical solution technique.

Experimental and numerical investigations on enclosure pressure effects on radiation and convection heat losses from two finite concentric cylinders using two radiation shields

The energy crisis has led humankind to drastically think about optimization of facilities which are in closed connection with energy resources. Therefore, optimization of thermal systems from heat transfer point of view, to decrease heat losses and therefore energy consumption, is an explicit goal in the field of thermal sciences. This work is about conjugate radiation and convection heat transfer in a cylindrical enclosure using two radiation shields, to decrease heat loss. The experimental study applies three different materials, namely aluminum, copper and steel, as radiation shields. Numerical investigation is performed and validated against experimental data, using three-dimensional finite volume method. Different positions for radiation shields within the enclosure are considered. Both experimental and modeling studies adopt two different enclosure pressures, i.e., 0.2 and 1.0 atm. The inner cylinder is assumed to have two different temperatures, i.e., 473 K and 673 K. Seventy six different experiments are carried out to capture the best heat reduction with different radiation shield materials, inner cylinder temperatures, enclosure pressures and radii for radiation shields. Results show that both enclosure pressure and radiation shield emissivity are responsible for reduction of the total heat loss from the inner cylinder.

Subadiabatic combustion of premixed gas in ceramic foam burner

During the combustion of low-concentration coal mine methane in a porous medium, subadiabatic combustion will occur with the upstream propagation of combustion waves. The lower concentration limit of methane combustion can be broadened, when the porous medium skeleton is preheated by the upstream propagation of combustion waves. In this study, an experimental apparatus of porous medium combustion was built and used to validate a numerical model. Then numerical tests were conducted to characterize the upstream propagation of combustion waves, and investigate the effects of many factors (e.g. methane working conditions, heat loss through walls, and dispersion effect) on the propagation. Results show that the upstream propagation of combustion waves is kept at an even velocity. During the propagation, the combustion products temperature at the burner outlet gradually decreases, while the peak temperature is unchanged. With the increase of methane concentration, the upstream propagation velocity of combustion waves and the peak temperature both increase. As the inlet gas velocity is increased, the upstream propagation velocity decreases but the peak temperature raises. As the heat loss through walls is increased, the upstream propagation velocity and the peak temperature both decrease. The CO emission quantity gradually decreases during the upstream propagation of combustion waves. With the increase of inlet velocity and heat loss through walls, the CO emission quantity within the same propagation period gradually increases. The NO emission quantity first increases slowly and then stabilizes during the upstream propagation of combustion waves. Moreover, with the increase of inlet velocity and decrease of heat loss through walls, the NO emission quantity within the same propagation period increases.

Influence of elevated pressure on blast-furnace performance

The influence of elevated pressure on the reduction processes and gas dynamics in the blast furnace is analyzed. With scope for greater air injection and greater upper and lower pressure differences, increase in gas pressure at the charge hole boosts furnace productivity and reduces the CO consumption in the reduction of iron from wustite, thanks to the briefer batch residence in the isothermal zone. The coke consumption is mainly affected by the decrease in heat losses with increase in productivity. The benefits of increasing the gas pressure at the charge hole are apparent in the operation of blast furnaces at OAO Novolipetskii Metallurgicheskii Kombinat.

ICOPE-15-1037 Development of Advanced Integrated coal Gasification Combined Cycle (A-IGCC) Power Generation Systems with a Gas Treating Unit

Advanced Integrated coal Gasification Combined Cycle (A-IGCC) systems have been proposed to obtain higher power generation efficiency than IGCC systems by recycling the exhaust heat from a gas turbine as the heat source of the gasifier. To date, the A-IGCC system including gasification, gas treating including CO_2 capturing and combined cycle power generation units has not been designed. In this study, the performances of A-IGCC systems with these units were evaluated by using process simulator Aspen Plus[○!R] ver. 7.2. Results showed the net thermal efficiencies of A-IGCC models with water gas shift (WGS) and CO_2 capturing units were lower than that of models without these units by 3.5-5.2% because of reduction in gas turbine and steam turbine outputs and additional heat and electricity input to CO_2 capturing unit. Net thermal efficiency of the A-IGCC system with the hot gas desulfurization unit was higher than that with the cold gas desulfurization unit (CGDU) by 1.4-3.1% owing to decrease in heat loss in coolers at CGDU, subsequent increase of heating value of fuel gas into the gas turbine combustors. The CO_2 emission factor can be reduced from 744-769 kg-CO_2/MWh to 117-137 kg-CO_2/MWh by capturing of approximately 85% of CO_2 after WGS.

Effect of the Gas-Phase Reaction on Hydrogen Micro-Combustion in a Pt/Γ-Al2O3 Catalytic Plane Channel with Detailed Chemical Kinetic Mechanisms

Hetero-/homogeneous micro-combustion of fuel-lean hydrogen–air mixtures in the plane channel containing a Pt/γ-Al2O3 catalyst washcoat was investigated numerically with detailed chemical kinetic mechanisms. The main theme of the paper is assessing the relative significance of the H2 gas-phase reaction as compared with catalytic reaction at different plane channel heights H, inlet mass fluxes J, and equivalence ratios ϕ in plane micro-channels. The numerical model of microcombustion was employed, which included detailed gas-phase and surface catalytic reaction mechanisms, heat transfer mechanisms, and diffusion of multicomponent species. In order to sustain micro-combustion of fuel-lean hydrogen–air mixtures over Pt/γ-Al2O3 in the range of operating conditions, the solid wall temperature of the micro-combustors was maintained at 1400 K. In plane micro-channels, as the channel dimension is decreased, the micro-combustion characteristics of hydrogen–air mixtures are significantly impacted due to radical and effective heat losses to the walls. However, the catalytic walls contribute to sustain the H2 gas-phase reaction in the micro-channels by decreasing heat losses to the walls due to the exothermic surface catalytic reaction, which also restrains the H2 gas-phase reaction by extracting radicals owing to typically high absorption rates of the above-mentioned species at the walls. Therefore, the detailed radical chain reaction mechanisms can be significantly changed by the presence of surface catalytic reaction (wall reaction), and the radical accumulation in the gas-phase can be restrained. In the present work, the effects of the above-mentioned three key parameters on the interaction between the surface catalytic and gas-phase reactions are discussed. For fuel-lean hydrogen–air mixtures, in each case, the limiting values of the plane channel height, inlet mass flux, and equivalence ratio beyond which the gas-phase reaction become negligible as compared with the surface catalytic reaction are explored. The computational results indicate that variation of the hydrogen–air inlet mass flux at constant inlet equivalence ratio and plane channel height alters the balance between the diffusive and convective mass fluxes. Finally, the equivalence ratio of the hydrogen–air mixtures significantly effects the contribution of the H2 gas-phase reactions to the entire H2 conversion.

지역난방 아파트에 대한 난방에너지 실측 및 시뮬레이션

Heating energy was measured in an apartment housing unit with a district heating system, varying the kind of hot water distributors. Ondol coils passing through a living room raised the temperature of the room where the heating was turned off. Including this characteristic of Ondol heating into the modeling, we performed simulations and showed a verification by comparison with the results of measurements. As a result, a main flow control method, which changes hot water flow rate supplied to a housing unit according to the thermal load, can reduce the supplied flow rate and lower the return temperature, compared with a constant flow method. That can result in decreased heat loss in utility-pipe conduits even though the heating energy supplied is almost the same. An outdoor reset control that raises the temperature of the supplied hot water if the outdoor temperature falls has the effect of a quicker response in heating than the reduced flow rate and return temperature.