Reduce Heat Loss Research Articles

Differences in heat losses between glazing of various emissivities related to night sky radiation: Experimental and numerical analysis

Radiation from cloudless night skies causes significant heat loss through glazing, resulting in higher heating costs. This study investigated the heat loss of glazing due to night-sky radiation as a function of its emissivity. A measuring apparatus comprising measuring stations mounted with glazing and two different emissivities was set up. The glazing losses and amount of energy radiated from the sky in the infrared region were measured. Additionally, to indicate the impact of other factors, a numerical model of glazing heat loss was prepared. A difference in temperature and heat losses between conventional glazing with an emissivity of 0.89 (29.47 W/m2) and coated glazing with an emissivity of 0.14 (5.43 W/m2) was observed. The temperature difference and heat losses were 54.26 % (1.28 °C) and 81.6 % (24.04 W/m2), respectively, in favour of the coated sample. The novelty of this study is the determination of heat losses from glazing of different emissivities due to radiation in the night sky under real conditions, with the indication of other factors. These results motivate further research on coated glazing to reduce heat loss. This numerical model can serve as a blueprint for examining similar applications.

The use of nanoparticles to enhance oil recovery

The article describes the actual problem of the introduction of nanotechnology in various fields of activity and existing technologies of the oil industry. The expediency of using nanotechnology to increase oil recovery, in the production of metal alloys to increase their strength characteristics and corrosion resistance, insulating coatings to reduce heat losses, lubricants that reduce wear of mating surfaces, in laboratory studies is shown. The results of the application of various nanotechnologies in the oil industry are presented.

ENHANCING CONVECTIVE HEAT LOSS REDUCTION IN FLAT-PLATE SOLAR COLLECTORS BY OPTIMAL INTEGRATION OF TRANSPARENT PARTITIONS IN THE AIR GAP

In a three-dimensional study, numerical simulations were carried out to quantify the natural convection heat transfer occurring within the air gap between the absorber and the glass cover of a thermal solar collector. The study explored various combinations of partition placement and spacing: partitions glued under the glass cover (PGG model), partitions glued at absorber (PGA model), and partitions suspended between the absorber plate and glass cover (PS model). Simulations were conducted with two partition spacing configurations of 0.14 m and 0.1 m. The primary aim was to identify cost-effective methods for reducing heat losses due to natural convection in the air gap while achieving higher absorption temperatures. The comprehensive numerical analysis included assessing flow patterns, temperature distribution, and heat transfer coefficients for each configuration. The findings revealed that using a partition spacing of 1.4 m resulted in complex and unstable outcomes, making comparisons between models difficult. However, decreasing the partition spacing to 0.1 m enhanced convective resistance, fostering temperature stability within the cavity. Nevertheless, the PGA model transitioned from unstable to stable flow, resulting in a notable temperature rise, making it the most effective configuration for minimizing thermal losses in the collector's frontal section. Additionally, the PGG model configuration exhibited promising performance. Meanwhile, the PS model experienced quasi-periodic cooling due to undulating flow patterns. This study stresses the importance of balancing uniform heating and stable flow in collector systems, highlighting the need for thorough 3D analyses. Strategic adjustments to partition placement and spacing can significantly improve solar collector design.

Integrated Janus interface solar evaporator for high efficiency solar distillation and interfacial desalination

Herein, an integrated Janus evaporator with hydrophobic top and hydrophilic bottom was reported. The solar evaporator employs melamine foam coated with polypyrrole (PPy) as substrate, in which the PPy coating enhances light absorption, heat transfer, and steam release while preventing salt deposition due to its hydrophobic nature. The hydrophilic bottom of the evaporator was obtained by local modification with sodium alginate, promoting upward water transport and reduce heat loss. The evaporation rate of the integrated Janus evaporator was maintained at 1.78 kg m-2h−1 when 10 % brine was evaporated for 12 h under 1 sunlight (1 kW m−2). The distillation remained at 1.68 kg m-2h−1 for 6 h and the photothermal conversion efficiency reached 99.0 %. Additionally, the evaporator has shown impressive results in treating wastewater. The combination of high efficiency, low cost, and easy preparation makes the Janus interface evaporator promising for the fabrication of solar steam generation systems suitable for practical desalination and wastewater treatment.

A trash-to-treasure strategy to upcycle abandoned masks to ultraelastic fiber aerogel

Masks are indispensable in our daily life, but the accumulation of abandoned masks has been increasing in landfills and incineration, causing serious environmental concerns. Here, we propose a trash-to-treasure strategy to reuse the hard-to-degrade polypropylene (PP) fibers in abandoned masks and introduce polyvinyl alcohol (PVA) as a binder to fabricate ultralight and ultraelastic PP fiber aerogel through a facile freeze-drying process. The fiber aerogel exhibits a highly porous structure with PP fibers closely bonded by PVA. Thanks to the overlapping structure of the PP fibers and the bonding effect of PVA, the fiber aerogel shows ultraelastic properties and can undergo repeated compression without any fatigue. The results further indicate that the fiber aerogel represents selective wetting behavior to oil and water with water contact angle of ca. 130° and oil contact angle of 0°, respectively. Owing to the highly porous, ultraelastic, and special wetting behaviors, the fiber aerogel demonstrates diverse potential applications in oil/water separation, thermal insulation, and pressure sensing. Briefly, the fiber aerogels can absorb diverse kinds of oils and organic solvents with an optimal oil absorption capacity high up to 27.5 g/g. The fiber aerogel can also be used as a heat-insulating material to reduce heat loss. Further, after being modified by conductive filler, the fiber aerogel can monitor various human activities in real time, including walking, knee bending, sitting, and lying. This study not only provides a new way to alleviate the difficulties of recycling abandoned masks but also proposes a novel strategy to prepare value-added multifunctional fiber aerogels.

Numerical analysis of the influence of radiation defects on the transport characteristics of a superconducting CORC-cable

Aim: development of a simultaneous model, calculation and analysis of heat losses of a superconducting CORC cable based on standard HTSC tapes and irradiated HTSC tapes in cyclic load modes for magnetic energy storage system.
 Methods: the CORC cable based on industrial original HTSC tapes and HTS tape with defects from irradiation is considered; to describe the electromagnetic and thermal characteristics of the system are used following methods: the concepts of the macroelectrodynamics, the fundamentals of the applied superconductivity, the finite element method are used; the calculation is implemented in the COMSOL Multiphysics.
 Results: a model was developed, the optimal cooling mode was determined in 5 load cycles, it was shown that the presence of artificial pinning centers can significantly improve the thermal stabilization of the system and leads to a reduction in heat losses with the considered cooling schemes.
 Conclusion: the results can be used in the development of the magnetic energy storage system based on high-temperature superconducting composites (HTS).

Synergistic thermal insulation enhancement of an Al2O3/MnO2 @ fumed silica composite thermal insulation coating with high-temperature resistance up to 1200 °C

Thermal insulating coatings effectively reduce heat loss, helping to save energy and reduce emissions. However, their thermal insulation performance decreases notably as temperature rises due to a single inhibition for heat transfer. Additionally, they have limited high-temperature resistance. To overcome these challenges. We developed a composite thermal insulation coating (CTIC). It was prepared through simple physical blending and can be effectively combined with various substrates. It achieves effective suppression of heat conduction and heat radiation, demonstrating excellent thermal insulation capabilities owing to the synergistic effect of fumed silica, Al2O3, and MnO2. It exhibited a low thermal conductivity of 0.0843 W/(m·K) at 500 °C. The 10 mm CTIC decreased the high temperature from 1008.9 °C to 339.5 °C. Moreover, the CTIC could withstand temperatures of up to 1200 °C. This work offers fresh insights into the design of thermal insulating coatings.

Impact of thermal swing piston top land coatings on gasoline engine performance and raw emissions

Upcoming legislations aim to significantly reduce carbon dioxide and hydrocarbon emissions compared to current regulations. Accordingly, options have to be evaluated to not only convert the raw emissions in a catalytic converter, but also to reduce the raw emissions from the combustion process in the first place. Therefore, thermal piston top land coatings, which lead to an oscillating piston surface temperature were investigated on a single cylinder research engine using a gasoline RON95E10 fuel. Measurements were conducted at a compression ratio of 12.2 and a long Miller intake event. In this manuscript the results achieved with yttria stabilized zirconia in comparison to an uncoated piston are displayed. Significant effects of the coatings on the indicated efficiency could be observed mainly at low engine speeds and loads due to the high share of fuel energy in the wall heat losses and incomplete combustion. At these operating points, the reduction of wall heat losses can almost be fully transferred into indicated efficiency, leading to an increase in indicated efficiency of 6.3% by the yttria stabilized zirconia coating. At higher engine speeds and loads, the advantage in indicated efficiency vanishes and a decrease of 0.5% can be observed. Near full load operation the indicated efficiency slightly lower. However, the effects of a thermal swing coating on combustion efficiency and wall heat losses strongly depend on the operation conditions.

COMBINED ENERGY SYSTEMS BASED ON RENEWABLE ENERGY SOURCES

Ensuring the quality of energy supply to remote regions is relevant for grid companies and the state. One of the solutions to this problem is the use of renewable energy sources to generate electrical energy. Given this, the article considers an integrated approach to designing combined autonomous energy systems of an individual residential building based on renewable energy sources with the complete replacement of traditional energy carriers. In addition to the combined power system, the proposed solution implies using an insulated facade of the building, which will reduce heat loss by 1.5 times, compared with an un-insulated building. to increase the reliability of the energy supply, the project provides for a wind power plant, a backup diesel generator station and a battery pack with an inverter. Estimated calculations have shown that the probability of failure of the power system of this configuration is 3%. The conducted ecological and economic justification of the use of an autonomous combined power system allows us to conclude that 2.1 tons of conventional fuel per year is saved and the payback of the energy supply system for a period of up to 8 years.

Effects of dimethyl ether blending on H2-fueled combustion characteristics and thermal improvement in fuel-lean condition

Micro-combustors play a pivotal role in micro powering system due to the potential for high energy density. However, addressing challenges such as incomplete combustion and high heat dissipation losses are essential for optimizing the working performance. So, the blended DME is proposed to micro-combustion, which acts as a promising oxygenated fuel with significant attention due to its higher reactivity, lower pollutant emissions, and carbon–neutral properties. However, the lack of dynamic models applicable to H2/DME fueled combustion in micro condition, so an optimized mechanism for blended H2/DME combustion is developed and validated. The results demonstrate that a reduced mechanism comprising 29 species and 106 reactions (M29-106*) can be commendably employed in micro H2/DME/air combustion simulation, according to the sensitivity analysis and reaction modification. Besides, investigation is conducted to explore micro-combustion characteristics of H2/DME/Air. The result shows that burning process and heat transfer are notably influenced by DME addition, leading to shifts in flame positions and adjustments in combustion reaction rates. So, DME addition enhances energy efficiency and modifies flame location through fluid field optimization and reduced heat loss. The thermal performance of the combustor is significantly improved with DME blending, resulting in higher radiative power and radiation efficiency. However, the choice of DME blending ratio must be carefully considered, as high blending ratios may compromise flame stability and lead to increased exhaust heat losses under fuel-lean conditions. Specifically, burning with 30 % DME addition achieves a radiative power of 20.24 W and a radiative efficiency of 40.57 % at the same chemical energy Ec = 49.9 W, which is 5.57 W and 11.17 % higher than that of pure H2-fueled combustion, respectively. These findings offer valuable insights for the design and optimization of micro-combustors, where compact and efficient power sources are required.

Технология снижения теплопотерь при транспортировке природного газа на компрессорных станциях

By 2050, the world's mineral reserves will account for 59-77% of the total number of energy sources. The share of renewable sources will grow to 20-30%, according to WEC research from 2013. Similar forecasts indicate that renewable energy sources are not enough to meet all the needs of humanity, and minerals will continue to play an important role. However, in order to meet the needs of the future, modern systems and technologies must be used much more efficiently. Gas is the purest of all natural resources, and the ongoing replacement of thermal systems from coal and oil to modern gas is an important step towards reducing greenhouse gases on the planet. Nevertheless, despite this transition, gas transmission systems are still not able to achieve their maximum efficiency, and despite their higher environmental friendliness, they still produce large volumes of harmful substances released into the atmosphere. The recovery of lost heat could increase efficiency and, at the same time, reduce emissions of harmful substances such as carbon dioxide and nitrogen oxides by replacing energy sources. Oil and gas companies are now increasingly moving to the production and use of hydrogen and methane-hydrogen mixtures. Thus, the recovery of lost heat is an incredibly valuable process for both production and nature. Nevertheless, technologies of this kind are only rarely used for processing exhaust gases at compressor stations due to low efficiency. A number of heat recovery technologies are considered to reduce heat loss during transportation of natural gas at compressor stations. The installation of a booster compressor station, which is designed for a specific pressure, is analyzed, adjusting it automatically, thereby reducing heat loss during gas transportation on compressors.

ҒИМАРАТТАРДЫҢ ҚОРШАУ ҚҰРЫЛЫМДАРЫ АРҚЫЛЫ ЖЫЛУ ШЫҒЫНЫН АЗАЙТУДЫ ЗЕРТТЕУ

One of the most important ways to save fuel and energy resources is to reduce heat losses through the building envelope. The use of high-performance heat-insulating, refractory materials makes it possible to create lightweight building envelopes that meet modern architectural requirements, allowing to reduce the operating costs of buildings by reducing heat loss. The purpose of this work is to study the causes of defects in operating buildings with enclosing structures made of sandwich panels to identify heat loss in the interface zones. The article addresses the issues of improving the nodal connections of enclosing structures made of sandwich panels, which is of great interest to designers in the construction of low-rise prefabricated buildings.

Assessing different glazing types for energy savings and CO2 reduction in a tropical climate: A comparative study

Energy efficiency in buildings and the mitigation of CO2 are key factors in the advancement of contemporary architecture, which includes aesthetic elements such as skylights, façades, and windows. Therefore, in this work the impact of different glazing types on energy savings and CO2 reduction was presented. A comparative analysis was conducted taking into account the climate-oriented approach in a specific climate context, Aw Köppen Climate Classification. Based on numerical results of the conjugate heat transfer in a two-dimensional geometry in a transient state, first, the glazing thermal performance under extreme weather conditions was evaluated, subsequently, an annual thermal evaluation was conducted. Triple glazing was highlighted as an effective option as it reduced heat loss by 56.5 % on the coldest day and reduced heat gain by 31.0 % on the warmest day in Mérida, Yucatán. Triple glazing also showed efficiency in reducing the total heat flux per unit area by 32.7 % under extreme temperature and solar radiation conditions, coldest day – south orientation and warmest day – west orientation. While glazing orientation showed a significant role in overheating, triple glazing decreased electricity consumption and CO2 emissions by 29 % per year, making it a leading choice for sustainable architecture.

Experimental investigation on the influence of portal-blocking speed on fire behaviors in tunnel structure

This work provides a series of fire tests in a 1/7 model tunnel to explore the influence of portal-blocking speed on tunnel fire behaviors. Burning rate, ceiling temperature, temperature distribution inside tunnel and thermal characteristic near tunnel portal are obtained and analyzed. Results shown that the comprehensive effect of portal-blocking speed on fire behavior is related to fuel area of fire source. For the fire scenario with small fuel area (Sfuel≤0.18 m2), the effect of blocking speed is not significant. While for the fire scenario with large fuel area (Sfuel≥0.54 m2), burning rate decreases rapidly, due to the blocking of tunnel portals. A critical blocking ratio existed due to the competitive between two action mechanisms of the reduction of air supplement and heat loss. The larger the fuel area is, the smaller the critical blocking ratio is. There is a delay effect on the burning suppression of fire source. For the fire scenario with large fuel area (Sfuel≥0.54 m2), the ceiling temperature distribution was more “uniform”, compared to that of the fire scenario with small fuel area (Sfuel≤0.18 m2). The faster blocking speed can make the ceiling temperature decay to a relatively low level earlier. The larger the fuel area is, the better the suppression effect of blocking strategy is. Earlier and faster blocking operation can effectively suppress the high temperature region, which is beneficial to the protection of tunnel lining.

Experimental study on thermal performance of high absorption latent heat storage plate (LHSP) in greenhouse

Phase change material (PCM) can effectively reduce temperature fluctuations in greenhouses and increase crop yields. Plastic greenhouses are a major form of facility agriculture in southern China, and there are no walls in it. Therefore, how to combine plastic greenhouses with PCM has become research hotspot. A new type of high absorption latent heat storage plate (LHSP) was proposed. That is to lay PCM plates on the north side of the plastic greenhouse vertically. To enhance solar energy utilization and reduce heat loss, solar high absorption and thermal insulation layer were respectively placed on the sunny side and shady side. Two greenhouses were constructed and LHSP was placed in one greenhouse as Case 1. After that, a solar high absorption film and thermal insulation layer were attached to the sunny side and the shady side as Case 2 and Case 3. The average air temperature of two greenhouses and the thermal performance of LHSP were compared under three cases. Results showed that, in Case 1, the LHSP can raise the average air temperature inside the greenhouse by 1.8–2.9 °C during the night. in Case 2 and 3, the average air temperature had a stable improvement of 1.6–2.2 °C and 1.8–2.1 °C respectively at night. Besides, in Case 2, the heat storage of LHSP on sunny side had increased by 26.2%. In Case 3, the total average heat loss of LHSP was reduced by 21.5% and the average heat release from sunny side had risen by up to 39.7%. The high absorption latent heat storage plate showed excellent thermal performance.

Thermal performance analysis of eccentric double-selective-coated parabolic trough receivers with flat upper surface

The Parabolic trough collector (PTC) system combined with molten salt energy storage system has gathered increasing attention owing to its advantages of high operating temperature and stable power output. However, the substantial heat loss experienced by parabolic through receivers (PTR) under high temperatures imposes limitations on the thermal efficiency and power generation potential of the PTC system. In this study, a novel eccentric double-selective-coated parabolic trough receiver is proposed. The upper surface of the receiver is flattened to further reduce radiation heat loss. Various distances from collector focus are explored to determine the most suitable opening angle of secondary selective coating, ensuring the highest thermal efficiency. The results show that, although the eccentricity causes partial optical loss, the reduced upper surface area and the resultant larger secondary coating opening angle contribute to a significant reduction in heat loss and an improved thermal efficiency of the novel receiver. The thermal efficiency of the new absorber can be improved by up to 20.59 % (under direct normal irradiance of 600W/m2 and a receiver surface temperature of 600 °C). Furthermore, the higher the emissivity and the lower the absorptivity of the solar selective coating, the better the performance of the novel absorber tube.

High-efficiency, thermal stable, and self-floating silver nanowires/Ti3C2Tx MXene/aramid nanofibers composite aerogel for photothermal water evaporation and antibacterial application

Interfacial solar steam generation shows great potential as a technology for seawater desalination. However, there are still considerable challenges in manufacturing photothermal evaporators with ultra-low thermal conductivity, mechanical robustness, and high-temperature resistance. Herein, we report Ag nanowires/Ti3C2Tx MXene/aramid nanofibers (Ag/Ti3C2Tx/ANFs) composite aerogel photothermal evaporators with internal three-dimensional (3D) micropores and a layered structure. The ANFs porous frame, with excellent mechanical properties and low thermal conductivity, allows abundant water transmission channels and reduces heat loss. Ti3C2Tx MXene and Ag NWs, known for their broadband absorption capability and antibacterial properties, enhance photothermal conversion efficiency. The Ag/Ti3C2Tx/ANFs composite aerogel distinguishes itself with a wide compression range (2 %∼60 %), remarkable light absorption capacity (96 %), and low thermal conductivity (0.49 W/mK), excellent thermal stability ensures the composite aerogel could withstand a wide temperature range from ∼500 °C to ∼196 °C. As expected, under one sun illumination, the Ag/Ti3C2Tx/ANFs composite aerogel presents a high evaporation rate of 2.21 kg m-2h−1 with an energy efficiency of 92 %. In addition, this evaporator composite aerogel exhibits outstanding and efficient salt tolerance, desalination, antibacterial properties, and heavy-metal ion wastewater purification capabilities. The unique evaporator structure presented here offers a new perspective for the structural design of next-generation, high-efficiency solar evaporators.

Multi-objective optimization of a solar photovoltaic thermal water collector using Grey Wolf Optimizer

Solar photovoltaic thermal (PV-T) collectors offer enhanced overall efficiency owing to reduced heat losses at the aperture plane and the potential for increased irradiance per unit area in comparison to larger prototypes. In spite of its promise, investigations into optimizing PV-T collector performance remain limited. This paper introduces a novel approach: the multi-objective optimization of a hybrid PV-T water system with a channel-type absorber design, utilizing the Grey Wolf Optimizer. The proposed approach employs regression models to depict key performance metrics—average thermal and electrical efficiencies. Optimal parameters, including rate of flow of cooling fluid, temperature at inlet, and slope of the solar panel, are determined and reported. In this paper, Grey Wolf Optimization algorithm, has been used to systematically explore the interaction of various PV-T parameter values. Optimal values, in line with the defined objective function(s) were obtained. This approach enabled the researchers to concurrently ascertain the comprehensive performance of the collector. Remarkably, the optimization process revealed a unique insight. Despite the inherently conflicting nature of thermal and electrical efficiencies as observed in single-objective optimization outcomes, the multi-objective MOGWO approach unveiled a solution where compromise was attained.

Cold Climate Challenges: Analysis of Heat Recovery Efficiency in Ventilation Systems

As building energy consumption gains ever-increasing attention worldwide, the focus on addressing it through the examination and optimization of efficient heat recovery solutions continues to intensify. With well-insulated and airtight buildings, the proportion of heating needs attributed to ventilation is growing, leading to the widespread integration and optimization of heat recovery solutions in mechanical ventilation systems. Heat recovery in ventilation is a highly efficient strategy for reducing heat losses and conserving energy. This study involves the investigation of a ventilation unit installed in an apartment situated in Riga, Latvia, as a practical examination of heat recovery system efficiency within the Latvian climate conditions, representing a cold climate region. The objective of this study was to examine the heat recovery efficiency of the ventilation system in the Latvian climate with variable outdoor and exhaust air parameters, given that the dry heat recovery efficiency is different from the actual heat recovery efficiency. The ventilation unit was equipped with a plate heat exchanger at an airflow rate of 105 m3/h. To evaluate heat recovery efficiency, extensive measurements of air temperature and relative humidity were conducted. The collected data was analyzed, employing statistical regression analysis to ensure measurement reliability and assess correlations. The findings indicated a strong correlation between variables such as heat content, moisture content, and sensible air parameters. It was observed that the actual heat recovery efficiency was 6% higher than the calculated dry efficiency, emphasizing the importance of considering real-world conditions in heat recovery assessments. Additionally, regression analysis demonstrated a positive linear correlation with a coefficient of 0.77, highlighting the dependency between actual measurements and the theoretical model. These quantitative outcomes provide essential insights for optimizing heat recovery systems and enhancing energy-efficient ventilation practices, especially in cold climate environments. Moreover, this study highlights the strong correlation between variables such as heat content, moisture content, and sensible air parameters. Findings offer essential insights for optimizing heat recovery systems and enhancing energy-efficient ventilation practices, especially in cold climate environments.

Is Dexmedetomidine Effective on Postoperative Shivering in Patients Undergoing General Anesthesia for an Appendectomy? A Double–Blind, Randomized Clinical Trial

Background: Postoperative shivering (PS) is a mechanism to reduce heat loss and is the most frequent complication during the recovery period after general anesthesia. Shivering can lead to discomfort and is even risky in many patients; therefore, prevention is important. Objectives: Our study aims to determine the effect of dexmedetomidine on preventing shivering after general anesthesia in appendectomy patients. Methods: The present double–blind, randomized clinical trial divided 90 appendectomy patients into two groups. Randomization was performed using the www.random.org website from the numbers of sequence generator option. One group received 0.5 µg/kg of dexmedetomidine before induction of general anesthesia, and another group received normal saline as a placebo. Shivering and other outcomes were checked in both groups. To find a 50% reduction of this incidence, based on alpha error of 5% and beta error of 20%, the sample size of 45 people was determined for each group. A P-value ≤ 0.05 was considered statistically significant. Results: In total, 63 (70%) patients were male, and 27 (30%) were female. There were no significant differences between the two groups in terms of age (P = 0.412), weight (P = 0.460), temperature of serum for fluid therapy (P = 0.315), fluid volume (P = 0.736), perioperative body temperature (P = 0.418), preoperative body temperature (P = 0.540), and room temperature (P = 0.310). The severity of shivering was significantly lower in the dexmedetomidine group (60%) than in the placebo group (P < 0.001). There was no significant difference according to gender and severity of shivering between the two groups (P > 0.05). Conclusions: This study suggests that the administration of dexmedetomidine can prevent postoperative shivering.