Linear concentrating solar power systems represent the most commonly installed types of concentrating solar power systems. These systems can be categorized into two types: parabolic trough collectors ...and linear Fresnel collectors. Due to their widespread use, they have garnered significant attention in different studies aiming to enhance their efficiency. This study conducts a review of studies conducted over the past decade, focusing on the various types of heat losses, a crucial parameter influencing the efficiency of linear concentrating solar power systems. It encompasses analytical, experimental, numerical, and hybrid studies related to heat losses in three subsystem classifications: simple tubular absorbers, compound parabolic collectors, and cavity receivers.
Heat loss literature can be categorized into four parts: three focused on reducing losses through enhancements in geometrical and structural configurations, the use of different heat transfer fluids, and various coating materials. The fourth category involves calculating or measuring heat loss alongside other important parameters in a proposed system. The assessment reveals that most studies (62.23% for parabolic trough collectors and 71.4% for linear Fresnel collectors) have focused on general studies to calculate heat loss. Approximately 14.89% of studies on heat loss mitigation for parabolic trough collectors concern geometry and coating materials, and 7.98% involve using different heat transfer fluids to reduce heat losses. In the case of linear Fresnel collectors, 27.14% of studies focus on geometry, while only 1.46% deal with heat transfer fluids, and no studies have been found regarding the use of materials to decrease heat losses in linear Fresnel collectors.
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•Heat loss is one of the most important parameters for LCSP systems.•Research on heat losses in LCSP systems is reviewed.•Geometry, HTF, and coating affect the heat losses of LCSP systems.•Geometrical configurations dominate research on LCSP heat loss mitigation.•Coating materials play the smallest role in LCSP heat loss research.
•Using infrared thermography, multiple thermal bridging heat loss can be easily estimated.•Installed window heat loss assessed by infrared thermography.•Results validated with hot box ...measurements.•Thermographic analysis results in good agreement with FE heat transfer and CFD simulations.
A major contribution to the global trend in reducing energy consumption can be made by improving the thermal performance of buildings. Minimization of heat loss via the building envelope is key to maximizing building energy efficiency. The building envelope contains different types of thermal bridging that must be accounted for while assessing the overall building envelope thermal performance. Multiple thermal bridges commonly occur and the distance between them determines the degree to which they interact thermally. To avoid overestimation of the linear thermal transmittance, it is important to account for interaction effects. Complex multiple thermal bridging occurs in window systems. The thermal performance of windows depends not only on the window performance itself but also on its installation into the wall. This study demonstrates an application of the quantitative infrared thermography technique to evaluate the heat lost via multiple thermal bridging. It is shown that using this methodology, the heat loss via multiple thermal bridges can be easily estimated in an existing building envelope, without any knowledge of its internal structure or material properties. For windows, it is demonstrated that jointly assessing the additional heat loss through the window and due to the installation of the window into the wall is a practical way to determine the actual heat loss caused by the presence of a window. A window thermal transmittance or M-value is introduced to quantify the total additional heat loss through the building element due to the presence of the window. The methodology was validated against experimental measurements taken on different specimens in a hot box device. Results from the thermographic analysis also co-related well with results from finite element heat transfer and computational fluid dynamics simulations.
Based on the design concept of a fourth-generation smart pipe network system, this paper innovatively proposes a new TOTS (Two-supply/One-return, triple pipe structure) arrangement method for ...district heating systems. Moreover, to accurately predict the heat loss due to the pipeline operation of the multi-pipe system, based on the multipole calculation method, a new heat loss theoretical analytical model for the TOTS was created; additionally, a corresponding three-dimensional numerical simulation model was established, which was analyzed and numerically solved. The results showed that in comparison with thermal loss data measured by Danfoss et al., the above analytical and numerical models have a high accuracy, and the deviation is within 2%. Additionally, through calculations, it was found that the distance between the heating pipes is an important factor that affects the total heat loss from the new multi-control heating system and the actual heat exchange between pipes.
•A new type of TOTS arrangement method is proposed.•A mathematical model of the heat loss for the multi-tube system was established.•A 3D numerical simulation model for the multi-pipe system was established.•The effects of the water supply pipes spacing on heat loss were studied.
PurposePerspiration and heat are produced by the body and must be eliminated to maintain a stable body temperature. Sweat, heat and air must pass through the fabric to be comfortable. The cloth ...absorbs sweat and then releases it, allowing the body to chill down. By capillary action, moisture is driven away from fabric pores or sucked out of yarns. Convectional air movement improves sweat drainage, which may aid in body temperature reduction. Clothing reduces the skin's ability to transport heat and moisture to the outside. Excessive moisture makes clothing stick to the skin, whereas excessive heat induces heat stress, making the user uncomfortable. Wet heat loss is significantly more difficult to understand than dry heat loss. The purpose of this study is to provided a good compilation of complete information on wet thermal comfort of textile and technological elements to be consider while constructing protective apparel.Design/methodology/approachThis paper aims to critically review studies on the thermal comfort of textiles in wet conditions and assess the results to guide future research.FindingsSeveral recent studies focused on wet textiles' impact on comfort. Moisture reduces the fabric's thermal insulation value while also altering its moisture characteristics. Moisture and heat conductivity were linked. Sweat and other factors impact fabric comfort. So, while evaluating a fabric's comfort, consider both external and inside moisture.Originality/valueThe systematic literature review in this research focuses on wet thermal comfort and technological elements to consider while constructing protective apparel.
High absorption of PV benefits heat collection in the daytime, but the heat loss to the space/environment because of its high emissivity also should be noticed. Although there are many papers ...investigating PVT, few of them cover the night behavior and negative running during late afternoon. This paper supplements detailed studies on related content to draw people's attention to the night and late-afternoon operation that helps better strategy establishment and less heat loss. From experiments, the clouds help hinder the PV radiant heat exchange with space. Under clear night, the PV bottom temperature can be 6.88 °C lower than air temperature and the water tank's bottom temperature drops 2.8 °C. Because of the fluid viscosity, no apparent temperature stratification and flow occur in the PVT water pipe, causing even PV temperature. The higher the water temperature, the easier the negative running occurs during late afternoon, although the irradiation is still high at 521W/m2. Heat loss power and energy are −199W and 1791 KJ from 15:10 to 17:40. Based on different regressed linear correlations of different PVT systems, the effect of water temperature, irradiation, and ambient temperature on the negative performance is also comparatively studied.
•Night behavior and negative running of PVT system are studied to avoid heat loss.•The clouds helps hinder the PV radiant heat exchange with the space.•PV bottom temperature can be 6.88 °C lower than ambient temperature.•Even the irradiation is still high at 521W/m2, negative running may still happen.•Negative operation is also comparatively studied based on different PVT and ambient.
•Currently, the air channel of SAH were mostly used serpentine flux paths composed of spoilers.•The sharp turn of 180° could create eddy current in the flow path and form “dead zone” during the flow ...process.•It reduces the ability of heat convection between the absorber plate and air in solar air heaters.•Therefore, the spiral solar air heaters (SAAH) is proposed in this paper, in which there is only a 90° turn of the channel.•Based on this design, pressure and power consumption of fans can be reduced and heat convection can be enhanced in SSAH.
A new type of solar air heaters was proposed by using the spiral shape of spoilers instead of the serpentine shape. The function of the spiral solar air heaters (SSAH), including heat collection efficiency, temperature differences between inlet and outlet, irradiance, and air volume were experimentally studied in this paper. According to the testing, the difference of temperature between inlet and outlet is related linearly to irradiation, and heat collection efficiency is related the quadratic function relationship to irradiation with a constant flux. Finally, the heat loss coefficient of the SSAH is determined by the normalized temperature to be 5.69 W m−2 K−1. Compared with the conventional and serpentine SAH, this kind of solar air heaters had a higher heat collection efficiency.
The convection heat loss from cavity receiver in parabolic dish solar thermal power system can significantly reduce the efficiency and consequently the cost effectiveness of the system. It is ...important to assess this heat loss and subsequently improve the thermal performance of the receiver. This paper aims to present a comprehensive review and systematic summarization of the state of the art in the research and progress in this area. The efforts include the convection heat loss mechanism, experimental and numerical investigations on the cavity receivers with varied shapes that have been considered up to date, and the Nusselt number correlations developed for convection heat loss prediction as well as the wind effect. One of the most important features of this paper is that it has covered numerous cavity literatures encountered in various other engineering systems, such as those in electronic cooling devices and buildings. The studies related to those applications may provide valuable information for the solar receiver design, which may otherwise be ignored by a solar system designer. Finally, future development directions and the issues that need to be further investigated are also suggested. It is believed that this comprehensive review will be beneficial to the design, simulation, performance assessment and applications of the solar parabolic dish cavity receivers.
Efficient and cost-effective solar steam generation requires self-floating evaporators which can convert light into heat, prevent unnecessary heat loss and greatly accelerate evaporation without ...solar concentrators. Currently, the most efficient evaporators (efficiency of ∼80% under 1 sun) are invariably built from inorganic materials, which are difficult to mold into monolithic sheets. Here, we present a new polymer which can be easily solution processed into a self-floating monolithic foam. The single-component foam can be used as an evaporator with an efficiency at 1 sun comparable to that of the best graphene-based evaporators. Even at 0.5 sun, the efficiency can reach 80%. Moreover, the foam is mechanically strong, thermally stable to 300 °C and chemically resistant to organic solvents.
In this paper, energy and exergy performance of an external type spiral tube receiver for a solar parabolic dish concentrator is experimentally analyzed and presented. Performance evaluation is done ...at three different radiation conditions. The receiver is tested in the temperature range of 30 °C–100 °C with water as heat transfer fluid and at a flow rate of 1.5 L per minute. The overall heat loss coefficient of the receiver estimated from the stagnation test is found to be 182 W/m2K. The average thermal and exergy efficiencies of the receiver was determined to be 56.21% and 5.45% respectively under an average beam radiation of 750 W/m2. The variation trend of thermal efficiency of receiver is similar to that of difference between temperature of the heat transfer fluid at receiver inlet and outlet. The results show that this light weight, low cost receiver has potential to be employed with solar parabolic dish concentrator for process heating applications.
•Spiral tube receiver is developed for solar parabolic dish concentrator.•Experimental performance analysis were carried out at different radiation levels.•The average thermal efficiency of the spiral tube receiver was obtained as 56.2%.•The receiver has potential to be used in the applications of temperature up to 100 °C.
The primary goal of this work is to examine the current materials for insulation utilized in the furnace of a refinery unit and to limit the waste heat dissipation through the radiant wall subbing ...with legitimate insulation materials. There are some exceptional materials whose properties are appropriate for reducing the heat loss in the furnace walls which could clearly decrease the heat loss through the radiant walls. By critical examination of these materials, the external temperature of the furnace is determined to prove that these materials can be utilized as substitution to those of the standard insulation materials.
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