Reduce Heat Loss Research Articles

Evaluation of effects of a green wall as a sustainable approach on reducing energy use in temperate and humid areas

Nowadays, with the advancement of construction technology, saving energy use of the building has been considered as one of the fields of environmental sustainability. The use of green cover and plants on the buildings is a suitable passive method that leads to the replace reduced urban green spaces and reduce the problems caused by the effect of the urban heat island (UHI) and improve the energy performance of buildings by reducing the indoor temperature, regulating humidity and creating thermal insulation. The objective of this study was to evaluate the reduction of energy consumption through the green walls of an educational building in Gorgan (Csa climate). For this purpose, first, a building designed on the university site, and the effects of two methods of constructing green walls by using three different plant species were simulated. For comparison, thermal data of a building with a direct green facade in the same climate was measured as an experimental sample, and the results were used in the simulation. The effects of using two methods of a green wall with three different plant species (Sedum, Parthenocissus tricuspidata, Hedera helix) were simulated, which Sedum has had better results than other species. The final results showed that the latent heat of the building is increased by green walls and less significant heat is generated in the environment than buildings without green cover. Also, in buildings with living green walls, compared to buildings with direct green facades, the thermal transmittance of the wall is reduced due to more material layers. The results show that some types of green walls reduce heat loss, and finally the total energy use of the building. The green wall has a more efficient effect on the buildings with a simple form and the limited number of interior spaces. In general, depending on the variables of each building, the use of green walls with plant species is different. It is better for a building before design, to determine the most appropriate method of constructing a green wall and plant species to reduce the energy usage according to project factors and climate type of the region.

Looking Critically at Heat Loss through Party Walls

Heat loss through party walls to outside (not the neighbouring dwelling) has received considerable attention in the UK, and this was flagged as a serious omission from the UK Building Regulations in 2010-12. There was evidence of significant heat loss between adjoined terraced or semi-detached new homes, which was increasingly important as heat loss from other parts of dwellings was being reduced. As a result, Building Regulations were changed so that other parts of the building envelope had to be improved in new homes to compensate for heat loss through the party wall. However, this empirical work based on measuring heat loss through the party walls of 55 UK dwellings indicates that fears about high heat loss through party walls may have been exaggerated. While a minority of dwellings (less than 10%) do suffer from a “thermal bypass” through the party wall, for the vast majority of existing homes with party walls, heat loss through the party wall is minimal. There may be a case for revising UK Building Regulations to reflect this new evidence, and for re-directing the efforts aimed at reducing heat loss through party walls towards other opportunities to improve the energy efficiency of dwellings.

Air curtains for reduction of natural convection heat loss from a heated plate: A numerical investigation

Concentrating solar power (CSP) plants encounter inefficiencies at all stages of electricity generation. Convection from the solar-thermal receiver is a significant mode of heat loss in CSP systems, and is challenging to mitigate. This study investigates the reduction of convection losses by using a planar jet that disrupts the buoyant flow arising from the heated surface of an external CSP receiver. An isothermal flat plate with a height of 1.8 m was used to model the receiver, and a planar jet air curtain with a nozzle thickness of 3 mm was introduced near the upper edge of the wall. A computational fluid dynamics model was first validated and subsequently implemented to conduct a parametric study on the heat transfer from the isothermal plate with an air curtain varying four parameters: jet speed, jet angle, plate temperature and plate inclination. The results showed that the air curtain generates a stagnation zone adjacent to the wall which successfully reduces local convective heat losses. The effectiveness of an air curtain is defined here as the relative reduction in the local heat loss due to the air curtain, compared to the case of natural convection alone. A local maximum of 31.2% effectiveness is achieved in the stagnation zone below the jet outlet for a vertical wall with a jet speed of 2.5 ms−1 and jet angle of 45∘. The air curtain effectiveness at the stagnation region was found to decrease with increasing jet speeds, whereas the effectiveness increased near the laminar-to-turbulent transition region with increasing jet speed. Smaller air curtain angles relative to the wall resulted in lower effectiveness. A 45∘ air curtain on a vertical wall can offer performance benefits that are similar in magnitude to inclining a wall from the vertical. A higher wall temperature was accompanied by better effectiveness near the jet outlet, particularly in the stagnation region, while lower wall temperatures produced higher effectiveness further from the jet. Therefore, an air curtain can be used to reduce convective heat losses locally from a heated flat surface, including potentially when applied to CSP receivers.

Experimental and simulation study on thermal effects and energy efficiency of a green wall in the humid condition of Rasht

The green wall systems have numerous benefits for buildings and urban spaces. In this study, the experimental analysis was conducted on an office building with a green wall in winter and summer times to assess the thermal effect in comparison with the bare wall through temperature and humidity data logger devices. The existing office building, which had a suitable condition, was used for evaluation. The purpose of this study was to investigate the thermal effect on the green wall. Moreover, the annual simulation was carried out to assessing energy efficiency on the green and bare walls using DesignBuilder V. 4.5 with actual office building specifications, in Rasht. The results showed that the heat transfer on the green and bare walls were measured at about 259.2 w/m2 and 241.92 w/m2, respectively, and in the summertime, about 66.5 w/m2 and 48.4 w/m2, respectively. Based on the simulation results, the green wall could reduce the heat transfer between the interior and exterior walls by about 7% and for winter, and about 27% for summertime. Further, it was observed that the green wall had about 42% have been more effective in reducing heat loss in the summertime. Eventually, the simulation indicated that the green wall has a uniform amount of consumption, which is estimated at a bare wall, and the green wall was 343 and 67 kWh per annum respectively and could have a better effective performance by about 80% on the energy efficiency in the humid climate.

EXERGY ANALYSIS OF A SINGLE-CYLINDER FOUR-STROKE GASOLINE ENGINE

In developing countries, the four-stroke single-cylinder gasoline engine finds wide use. Motorcycles, tricycles and household machines like vegetable grinding machines are but a few of the machinery which run on this engine. Researchers have found that this engine is inefficient and consumes a lot of fuel, in light of sustainability and energy efficiency, this study aimed to perform an exergy analysis of a single-cylinder 4-stroke gasoline engine to determine how best its efficiency can be improved. Parameters such as brake thermal power, exergy efficiency, the quantity of exergy destruction and the component of the engine which is the most influential on its efficiency were determined while varying the engine’s torque. A G200K1 Honda engine was used as the study material. At the lowest tested torque of 9.4Nm, a corresponding brake power output of 2.4609kW and efficiency of 17.07% was measured, while at a higher torque 9.70Nm, a corresponding brake power output of 2.5395kW and efficiency of 17.62% was measured. It was also found that for every 1.06% rise in torque there is a corresponding 1.80% rise in brake power and exergy efficiency. It was concluded from the findings that the bulk of energy waste in the system comes from the high-temperature gas released from the engine’s exhaust. For the overall efficiency of four-stroke single-cylinder gasoline engines to be improved, the exergy destruction due to combustion should be minimised by optimizing the combustion temperature and reducing heat loss from the combustion chamber.

Self-similar solutions for resistive diffusion, Ohmic heating, and Ettingshausen effects in plasmas of arbitrary β

Magneto-inertial fusion (MIF) approaches, such as the MagLIF experiment, use magnetic fields in dense plasma to suppress cross-field thermal conduction, attempting to reduce heat loss and trap alpha particles to achieve ignition. However, the magnetic field can introduce other transport effects, some of which are deleterious. An understanding of these processes is thus crucial for accurate modeling of MIF. We generalize past work exploiting self-similar solutions to describe transport processes in planar geometry and compare the model to the radiation-magnetohydrodynamics (MHDs) code Chimera. We solve the 1D extended MHD equations under pressure balance, making no assumptions about the ratio of magnetic and thermal pressures in the plasma. The resulting ordinary differential equation (ODE) boundary value problem is solved using a shooting method, combining an implicit ODE solver and a Newton–Raphson root finder. We show that the Nernst effect dominates over resistive diffusion in high β plasma, but its significance is reduced as the β decreases. On the other hand, we find that Ettingshausen and Ohmic heating effects are dominant in low β plasma and can be observable in even order unity β plasma, though in the presence of a strong temperature gradient heat conduction remains dominant. We then present a test problem for the Ohmic heating and Ettingshausen effects which will be useful to validate codes modeling these effects. We also observe that the Ettingshausen effect plays a role in preventing temperature separation when Ohmic heating is strong. Neglecting this term may lead to overestimates for the electron temperature at a vacuum–plasma interface, such as at the edge of a z-pinch. The model developed can be used to provide test problems with arbitrary boundary conditions for magnetohydrodynamics codes with the ability to freely switch on terms to compare their individual implementations.

Design, simulation and measurement of a single-band high-transmittance all-dielectric metamaterial filter

Metamaterial filters are widely used in various photo-electronic devices because of the rich resonance behaviors. Transmission and thermal resonance properties are important factors to measure the performance of photo-electronic devices based on metamaterial filters. It is important to accurate measure the thermal resonance performance of the metasurface to improve the thermal management of these photo-electronic devices, reduce heat loss, and delay device damage. In this paper, a metamaterial filter is proposed and verified in the 0.5–3.0 THz range. A transmission peak of 94.3% at resonance frequency 1.43 THz is achieved by the proposed filter samples at room temperature. The thermal diffusivity (8.28) and thermal resistance (7.58) of the metasurface are measured by using thermal pulses, which can be improved effectively by separating the sample and the standard substrate with a resin layer (TIM layer). The intensities of the applied electric field and heat pulse have significant influence on the thermal diffusivity and thermal resistance of the metasurface. When the electric field exceeds 42 km/mm or the heat pulse exceeds 1.3 mJ, the thermal diffusivity and resistance of the metasurface appear obvious divergence phenomenon. Moreover, the thermal resonance properties of the proposed sample is higher than that of the stacked plate structure.

Design Evaluation of a Next-Generation High-Temperature Particle Receiver for Concentrating Solar Thermal Applications

High-temperature particle receivers are being developed to achieve temperatures in excess of 700 °C for advanced power cycles and solar thermochemical processes. This paper describes designs and features of a falling particle receiver system that has been evaluated and tested at the National Solar Thermal Test Facility at Sandia National Laboratories. These advanced designs are intended to reduce heat losses and increase the thermal efficiency. Novel features include aperture covers, active air flow, particle flow obstructions, and optimized receiver shapes that minimize advective heat losses, increase particle curtain opacity and uniformity, and reduce cavity wall temperatures. Control systems are implemented in recent on-sun tests to maintain a desired particle outlet temperature using an automated closed-loop proportional–integral–derivative controller. These tests demonstrate the ability to achieve and maintain particle outlet temperatures approaching 800 °C with efficiencies between 60 and 90%, depending on incident power, mass flow, and environmental conditions. Lessons learned regarding the testing of design features and overall receiver operation are also presented.

Novel nanofluid based efficient solar vaporization systems with applications in desalination and wastewater treatment

The current work proposes a new strategy to improve solar evaporation efficiency and explore the real applications of volumetric solar evaporation device in desalination and wastewater treatment. Nanofluid based volumetric solar evaporation system is efficient to enhance the absorbance of solar irradiation. However, the solar evaporation efficiencies are relatively low. There is a need to investigate the fundamentals of the limitation and find a new strategy to improve the solar evaporation efficiency. In this paper, a novel device containing tungsten carbide nanofluids as work fluids is designed for the first time to reduce heat loss towards the bulk water, improve the stability of nanofluids, and avoid contamination of nanoparticles. The results show that tungsten carbide nanofluids of 0.3 wt% can harvest 99% of the incident solar energy within 1 cm penetration distance. The photothermal conversion efficiency is 97.7%. The novel device gives an evaporation rate of 1.235 kg m−2 h−1 and reached solar evaporation efficiency of 74.9% under 1-sun irradiation. The applications in desalination and wastewater treatment show that the ion rejection rate of seawater is higher than 99.99%, and the content of heavy metal ion is significantly lower than that in the World Health Organization drinking-water standard.

Heat transfer study of four nested helical coils inside an absorption heat transformer

ABSTRACT This paper shows the design and experimental analysis of a dual generator/condenser component for an absorption heat transformer (AHT) of 2 kW operating with H2O/LiBr, and heat exchangers with four nested helical coils in series. This design shows a compaction ratio of 5.26 × 104 Wm−3/K in the generator and 1.58 × 104 Wm−3/ K in the condenser (higher than in the literature). This AHT can research a gross temperature lift of up to 24.9 K and coefficient of performance of 0.44. The desorption and condensation processes developed under the new arrangement reduce the sizing and installation area, and reduce heat losses, tube friction, and stability time.

Photo‐thermal conversion performance of mono MWCNT and hybrid MWCNT‐TiN nanofluids in direct absorption solar collectors

Solar energy is being widely investigated due to its abundant, renewable, and clean features. Photo-thermal conversion in solar collectors is a direct approach for harvesting solar energy. Compared to the commonly used surface-based solar collectors (SSCs), nanofluid-based direct absorption solar collectors (DASCs) are more efficient. In this work, water-based mono MWCNT and hybrid MWCNT-TiN nanofluids were prepared through a two-step method, aiming at light absorption enhancement of nanofluids for applications in DASCs. The optical and photo-thermal conversion performance of the MWCNT nanofluids was firstly evaluated. The results showed that the MWCNT nanofluids presented high solar absorption capability, and the highest photo-thermal conversion efficiency was obtained at 10 ppm. The TiN nanoparticles were subsequently incorporated to form the hybrid MWCNT-TiN nanofluids. The absorption performance of the hybrid nanofluids was further enhanced. The highest efficiency of the hybrid MWCNT-TiN nanofluids was achieved at the TiN mass fraction of 10 ppm, which was about 6.9%, 6.0%, and 3.8% higher than that of the MWCNT nanofluid at 2000, 4000, and 6000 seconds due to the localized surface plasmon resonance (LSPR) effect of TiN nanoparticles. It was also found that the collector efficiency dropped rapidly with the prolonged irradiation time owing to the convection and radiation heat loss at the elevated temperature. Therefore, effective measures should also be taken to reduce heat loss to maintain high photo-thermal conversion efficiency.

The influence of mineral inclusions on the heat efficiency of the enclosing construction from wood-cement composite in the rural house building

Reducing the cost of maintaining housing objects inevitably leads to the development of energy-saving technologies and building materials. Cost reduction is achieved by reducing heat losses through walls and floors of buildings and structures. Wood-cement composite materials are attractive not only from the point of view of energy saving and reducing construction costs, but also as materials in the production of which woodworking waste is used, therefore, the problem of complex waste-free use of raw materials is solved. In the course of the research, the influence of mineral inclusions on the indicators of the thermal efficiency of enclosing structures made of wood-cement composite (wood concrete and sawdust concrete) was determined. The work was based on the use of physical modeling methods (finite element method) implemented in the Elcut software package. The value of the heat loss indicator, depending on the type of wood-cement composite and operating conditions, was 34.2…. 54.8 W/(m2·°C). The indicator of resistance to heat transfer is 0.58 … 2.2 (m2·°C)/W. The presence of mineral inclusions worsens the thermal performance of the enclosing structure by an average of 7%. The results obtained can be used in the design and operation of building structures made of wood-cement composites.

Electronics and waste material recycler energy-efficient electric furnace system

Steel and iron manufacturing, nonferrous metal production, glass production, ceramic processing, and the creation of various forms of items all rely on material production. High temperatures are used in furnaces for smelting and recycling. An electric furnace may be suitable as natural gas is not widely available everywhere. Bangladesh's melting and recycling machinery is powered by a traditional gas furnace, which is expensive and inefficient. By recycling and reusing scrap metal, natural ore, and alloys, the suggested model has the potential to revolutionize, reducing the build-up of natural energy alloys, gas, and ores. The proposed electric furnace has an enclosed form and uses electricity to generate heat efficiently. To melt reusable metals, electronic materials, and waste materials, an electric furnace system based on the Arduino Mega as an alternative to the PID controller with Solid State Relay has been developed, which will manage and control the temperature around 1350 °C (1623.15 K or 2462 °F) by collecting data from the furnace thermostat. This model is made of stainless steel, with a steel frame for the outer shape of the furnace body and control box, a ventilation hole for removing hot gas from inside the furnace, an airtight door for opening the furnace chamber, a digital temperature controller with a furnace B-type thermocouple for measuring and controlling temperature, an ELB for safety, and heat insulation materials with a Nichrome80 heating element in the chamber. The model uses an Arduino Mega to regulate power and temperature while reducing heat loss via the furnace body, reducing time delays, and increasing efficiency. The findings demonstrate that the desired temperature is reached fast and with less electricity than the other electric furnaces, indicating that the model is energy efficient. The smelting temperature for aluminum, copper and other similar materials has been effectively covered. This model has better efficiency since there is no heat loss. The melting and recycling processes will help the furnace-related sectors the most. However, this could be especially beneficial for a developing economy like Bangladesh, where gas and fuel are expensive. • This article develops an electric furnace system that may be operated manually (PID) or automatically (Arduino Mega). • The proposed system is capable of producing temperatures of around 1350 °C (1623.15 K or 2462 °F). • Compared to other traditional furnace systems, the suggested furnace system can attain the desired melting temperature in short period. • When the thermocouple circuit reaches the predetermined melting temperature, the control system switches it off automatically. • Reduce melting cost, heat loss, increase efficiency, carries more benefits for the melting/recycling for reusing waste materials.

Significant energy saving in industrial natural draught furnace: A model-based investigation

• Model based simulation is carried out for industrial scale natural drought cabin furnace. • Aspen Hysys and exchanger design rigorous (EDR) program used for modelling and simulation. • Sensitivity analysis was carried out to predict the impact of several parameters on the furnace efficiency. • The study shows potential of significant savings in energy, operational cost and carbon footprint. In all industrial petrochemical plants and refineries, the furnace is the source of heat resulting from fuel combustion with air. The model-based furnace simulation is considered one of the efficient methods help to reduce the energy loss and maintain fixed refinery revenues, conserving energy, and finally reducing external fuel consumption and total fuel cost. In this paper, a model-based simulation is carried out for a natural air draught industrial scale furnace related to Liquified Petroleum Gas (LPG) production plant in Libya to thoroughly investigate the most responsible factors in lowering the furnace butane exit temperature, which is supposed to be two degrees Fahrenheit higher than inlet temperature. Therefore, to resolve this industrial problem, Aspen Hysys V10, coupling with EDR (exchanger design and rating) is used to carry out rigorous model-based simulation. This is specifically used to assess the impact of heat loss from inside the firebox to the surrounding medium and heat loss from the furnace stack and walls, besides the effect of excess air on the furnace efficiency. Furthermore, this research intends to verify whether the operating conditions, such as furnace tubes inlet flow rate, temperature and pumping pressure, are conforming to the upstream process design specifications or need to be adjusted. The results confirm that increasing furnace outlet temperature two degrees Fahrenheit from off specification 190 °F instead of 184 °F is successfully achieved by decreasing upstream stream flowrate 25% below the operating value and cutback excess air gradually until 20%. Also, the results clarify the necessity of increasing the flue gas temperature by 7% over design condition, to gain a significant reduction of heat loss of 31.6% and reach as low as 35.5 MBtu/hr. This improvement is achieved using optimum operating conditions of an excess air of 20%, and flue gas oxygen content of 3.3% delivered to stack. Accordingly, the furnace efficiency has been increased by 18% to hit 58.9%. Furthermore, the heat loss from the furnace walls can be also reduced by 68% from 5.41 MBtu/hr to 1.7 MBtu/hr by increasing the refractory wall thickness to 6 in., which entails an increase in the furnace efficiency by 3.66% to reach 58.96%. Decreasing the heat loss fraction through the refractory wall, pip doors, expansion windows and refractory hair cracks would also increase the efficiency by 21% to reach a high of 59.7%. Accordingly, a significant reduction in daily fuel consumption is observed, which costs 1.7 M$ per year. The outcomes of this research clearly show the potential of reducing the operation and maintenance costs significantly.

Waste heat recovery potential in residential apartment buildings in Finland's Kymenlaakso region by using mechanical exhaust air ventilation and heat pumps

With the growing share of ventilation heat loads, the heat recovery over the mechanical ventilation systems appears as one of the key solutions to reduce heat loss and generate energy savings. Finland's long-term renovation strategy aims for a highly energy-efficient and almost carbon-free building stock by 2050. One of the greatest potentials for energy savings relates to those built between the 1960s and 1980s where no heat recovery exists. This study addresses the wasted heat potential of apartment buildings in the Kymenlaakso region in Finland and how EAHPs can utilize it. The wasted heat potential was mapped by selecting buildings of different ages in Kotka from the 1950s to 2010 and for which the thermal energy balance was determined. The apartment buildings with mechanical exhaust ventilation in Kymenlaakso were surveyed. If all the mapped exhaust air waste energy could be utilized by EAHPs, it could produce the thermal energy combined from different decades up to 18.7 GWh/a in Kotka and 36.8 GWh/a in Kouvola. The calculated annual reduction in CO 2 emissions might be about 590 and 944 tCO 2 in Kotka and Kouvola, respectively. The calculated payback periods varied from 7 to 13 years for the selected buildings.

An experimental investigation of the effectiveness of partially and fully submerged metal hollow-fins and jute cloth wick-fins on the performance of a dual-basin single-slope solar still

The rapid growth of the population and industrialization have caused a global crisis for potable water, which has triggered researchers to propose an alternative solution to the problem. Solar still is a solar energy-based device confronting the problem of low productivity. The prime objective of the present study is to investigate the effectiveness of hollow-fins and wick-fins on the performance of dual-basin single-slope solar still. The performance of solar still with hollow-fins, wick-fins, and without fins has been compared in two sets of experiments for partially and fully submerged cases. The distillate outputs from stills for partially submerged fins were 4.2313 L/m2 (8.96% higher) with wick-fins, 4.0733 L/m2 (4.89% higher) without fins, and 3.8833 L/m2 with hollow-fins. The wick-fins improve the performance of the solar still by increasing the evaporation surface and rate of evaporation through capillary action. The distillate outputs from stills for fully submerged fins were 3.6554 L/m2 (3.91% higher) with wick-fins, 3.8534 L/m2 (9.54% higher) without fins, and 3.5179 L/m2 with hollow-fins. The reason for the higher performance of still without fins are the highest temperature of the lower basin; reduced heat loss due to increased heat storage capacity of brackish water; a lower temperature difference between the lower basin and saline water that increases evaporation of brackish water in the lower basin; the highest temperature difference between saline water and the upper basin glass cover that enhances the condensation rate of water vapour in the upper basin. The still with wick-fins proved to be the most efficient from the performance and economic point of view for partially submerged fins, while the still without fins proved to be the most efficient for fully submerged fins.

The effect of ignition delay time on the explosion behavior in non-uniform hydrogen-air mixtures

The purpose of this study is to examine the explosion characteristics of non-uniform hydrogen-air mixtures with turbulent mixing. In the experiment, hydrogen is first filled into a 20 L spherical chamber to a desired initial pressure, then air is introduced into the same chamber through a fast response solenoid valve, by adjusting the ignition delay time (td), i.e., the time period between the end of air injection and the action of ignition, the turbulent mixing strengthen (or called uniformity of hydrogen-air mixture) is then changed. The experimental results show that the explosions are overall enhanced as td decreases, which indicates that turbulence plays a leading role in enhancing the explosion behaviors. In addition, it is found that the effect of turbulence on pmax is more prominent in end-wall ignition than that in center ignition. This is because the heat loss per unit time is higher in end-wall ignition due to the flame front continuously contacts with inner wall of the chamber throughout the explosion process, although the explosion duration time te for both ignition cases is reduced when turbulence is introduced, heat loss reduction for end-wall ignition is generally larger than that in center ignition. Lately, a systematical analysis of the turbulent effect associated with various equivalence ratios on the explosion characteristics is conducted in end-wall ignition. Those experimental results illustrate that the turbulence-enhancing influence is more noticeable when hydrogen-air mixtures move toward the lower explosion limit. However, no significant influence of turbulence on explosion process can be found as combustible mixtures tend to the fuel-rich side. This is mainly because that when hydrogen-air mixtures tend to fuel-rich side, τe reduction caused by the presence of turbulence is relatively weak as compared with that under quiescent condition, resulting in heat loss during explosion process changes slightly, hence there is no significant impact on explosion parameters.

Effects of Outer Shell Fabric Color, Smoke Contamination, and Washing on Heat Loss through Turnout Suit Systems

Firefighters frequently have to work in direct solar radiant heat. To reduce firefighter heat stress, the influence of turnout garment properties on heat gain from solar radiation must be understood. This research studied the effects of color, texture, washing, and contamination of outer shell fabrics on heat loss through firefighter turnout fabric materials in simulated solar exposures. It showed that solar radiation could be a major factor in heat loss through turnout suits. Solar radiation equivalent to a sunny day completely reversed heat exchange through the turnout fabric systems, converting a heat loss of about 240 W/m2 to a heat gain exceeding 100 W/m2. Solar radiation caused turnout fabric systems to dry out and this decreased the performance of turnout systems that incorporated bi-component moisture barriers. Most significantly, the color of the outer shell had a major influence on lowering turnout heat loss in solar exposures. Composites with a black-dyed outer shell absorbed more solar energy than composites with lighter colored shell materials. Soot and fire-ground contaminants present on turnout outer shell fabrics also reduced heat loss under solar exposure. The findings of this study answered long-standing questions about the importance of turnout fabric color on heat exchange with the environment. The results provide additional motivation for efficient turnout cleaning practices, not only to reduce potentially toxic exposure to smoke contaminants, but to reduce turnout-gear-related heat strain on firefighters.

Investigation of the influence of design parameters on thermal processes in a blast furnace tuyere using ANSYS software

It is known that the maximum heat losses in a water­cooled tuyere of a blast furnace are in the blowing channel. An effective way to reduce them is to install a heat­insulating ceramic insert. Such inserts installed in the inner cup of air tuyeres for the blast furnace no. 5 of PJSC “Severstal” reduce heat losses through the tuyere by 30 %, and inserts, which, in addition, insulate most of the inner surface of the snout part, further reduce heat losses through the tuyere by 26.2 %. The ANSYS software was used to study the effect of design parameters on thermal processes in a blast furnace tuyere with heat­insulating insert. To make the simulation more realistic the entire air tuyere, including water­cooling circuit, was considered as the modeling object. Protrusion of the insert into the blowing channel by 2 mm improves the mixing of natural gas and blast, promotes gas combustion, which leads to an increase in heat losses through the blowing channel and a decrease in resistance of the insert. To increase durability of the insert and reduce heat losses through the blowing channel, it is justified to use an elongated insert with a thickness varying from 13 to 8 mm in the blowing direction, which does not protrude into the blowing channel, having an angle between the normal to the side of the inner cup and the axis of the hole for natural gas supplying about 30°. It is shown that to obtain the maximum heat content of the blast, which is influenced by the combustion of natural gas and heat losses with cooling water in the blowing channel, it is preferable to have an elongated insert of variable thickness, varying from 10 to 8 mm in the blowing direction, and axis of the hole for natural gas supply perpendicular to the wall of the inner cup.

Pipe Insulation Evaluation for Low-Temperature District Heating Implementation in South Korea

Future energy systems will comprise 100% renewable energy and involve high integration of energy systems. District heating (DH) and cooling systems will be an undeniable part of future energy systems, as they facilitate high-efficiency, low-cost, and clean production. Low-temperature district heating (LTDH) is one of the candidates for future district heating systems, where the supply temperature is 60°C or below. Reducing heat losses from the pipe network in DH systems is challenging. Improving the insulation standards in DH pipes can decrease heat and temperature losses in the pipe networks. This study employs computational fluid dynamics to evaluate the optimum insulation thickness based on the material and digging costs in South Korea. A micro hybrid DH system with natural gas run fuel cell, heat pump and solar thermal is proposed in this study. An evaluation of the system with a 500 m pipe network system supplying hot water at 60°C with polyethylene, ethylene propylene diene monomer rubber, and polyurethane as insulation materials using ANSYS Fluent 17.2 shows that the heat losses are minimal when using PU foams. A cost estimation analysis showed that 32 mm was the optimum insulation thickness for achieving heat losses below 20 W/m and minimum material and digging costs when burring the pipeline network in the ground.