Increased Heat Loss Research Articles

Experimental facilitation of heat loss affects work rate and innate immune function in a breeding passerine bird.

The capacity to get rid of excess heat produced during hard work is a possible constraint on parental effort during reproduction [heat dissipation limit (HDL) theory]. We released hard-working blue tits (Cyanistes caeruleus) from this constraint by experimentally removing ventral plumage. We then assessed whether this changed their reproductive effort (feeding rate and nestling size) and levels of self-maintenance (change in body mass and innate immune function). Feather-clipped females reduced the number of feeding visits and increased levels of constitutive innate immunity compared with unclipped females but did not fledge smaller nestlings. Thus, they increased self-maintenance without compromising current reproductive output. In contrast, feather clipping did not affect the number of feeding visits or innate immune function in males, despite increased heat loss rate. Our results show that analyses of physiological parameters, such as constitutive innate immune function, can be important when trying to understand sources of variation in investment in self-maintenance versus reproductive effort and that risk of overheating can influence innate immune function during reproduction.

RnProbe: A LoRa-Enabled IoT Edge Device for Integrated Radon Risk Management

Radon is a naturally occurring radioactive gas that can easily accumulate in indoor environments. According to the World Health Organization (WHO), radon gas is the second largest risk factor associated with lung cancer, after tobacco smoking. People spend at least half their life inside buildings, which are becoming increasingly more hermetic due to the pursuit of high energy efficiency - an increase in ventilation rates tends to increase heat losses. In this context, energy efficiency and Indoor Air Quality (IAQ) concepts, if not studied in a balanced way, can move in opposite directions. The introduction of Internet of Things (IoT) technologies for continuous assessment of the IAQ can help to achieve an optimally integrated balance between them. This article focus on the specification and design of the RnProbe, an IoT Edge Device developed under the scope of the RnMonitor R&D project whose main objective was the specification and development of a Cyber-Physical System (CPS) for integrated Radon Risk Management in public buildings, such as schools, kindergartens, offices, and hospitals, that are restricted to regular occupancy schedules, so that policymakers and building managers can reduce public health risks associated with the exposure to this pollutant. The device collects, aggregates, and transmits up to the cloud, several indoor environmental parameters. When combined these measurements are used to perform specific mitigation actions in the building, to improve IAQ.

Exposure to artificial wind increases energy intake and reproductive performance of female Swiss mice (Mus musculus) in hot temperatures.

High temperatures and heatwaves are rapidly emerging as an important threat to many aspects of physiology and behavior in females during lactation. The body's capacity to dissipate heat is reduced by high ambient temperatures, increasing the risk of hyperthermia. Exposure to wind, a pervasive environmental factor for most terrestrial animals, is known to increase heat loss, but its effects on the reproductive performance of small mammals remains unclear. In the present study, the effects of wind on the energy budgets, resting metabolic rate and milk energy output (MEO) were measured in lactating Swiss mice at 21 and 32.5°C. Females kept at 32.5°C had a significantly lower resting metabolic rate, food intake and MEO, and lighter offspring, than those kept at 21°C. However, exposure to wind increased the asymptotic food intake of females kept at 32.5°C by 22.5% (P<0.01), their MEO by 20.7% (P<0.05) and their litter mass by 17.6% (P<0.05). The body temperature of females kept at 32.5°C was significantly higher during lactation than that of females kept at 21°C, but this difference was reduced by exposure to wind. These findings suggest that exposure to wind considerably improves reproductive performance, increasing the fitness of small mammals while undergoing hot temperatures during heatwaves.

Two lines of evidence for physiological control of insensible evaporative water loss by a tiny marsupial.

We present two independent lines of evidence that a tiny dasyurid marsupial, the ningaui (Ningaui spp.), has acute physiological control of its insensible evaporative water loss below and within thermoneutrality. Perturbation of the driving force for evaporation by varying relative humidity, and therefore the water vapour pressure deficit between the animal and the ambient air, does not have the expected physical effect on evaporative water loss. Exposure to a helox atmosphere also does not have the expected physical effect of increasing evaporative water loss for live ningauis (despite it having the expected effect of increasing heat loss for live ningauis), but increases evaporative water loss for dead ningauis. We discuss the relative advantages and disadvantages of both experimental approaches for demonstrating physiological control of insensible evaporative water loss. An appreciation of physiological control is important because insensible evaporative water loss contributes to both water and heat balance, is clearly under environmental selection pressure, and potentially impacts the distribution of endotherms and their response to environmental change.

Perfecting technology of winter concreting of cast-in-situ columns

The article deals with an analysis of the existing systems of the heating method of reinforced concrete structures. It is demonstrated that, concreting of rectangular columns, the area of angles is characterized by a lower concrete quality than in other areas, which causes extensive damage in indicated zones. To remove the existing limitations, the formwork design for concreting of cast-in-situ columns is offered in the article. It was established that during the removal of column formwork one can often observe palled angles with reinforcement uncovering. Corners are the most vulnerable parts under impact forces or static loads during the exploitation. Repair and restoration of the exterior view and protective properties of concrete in column corners often require using materials or repair methods, which increase the cost of construction. The reasons of concrete lower quality are in the incompact joints of formwork elements and the chilled temperature of concrete hardening. Furthermore, the reason is in low temperature in columns corners. It is the consequence of the deficiency of existing heating systems ignores the irregularity of heating proper emission of the heat and increased heat loss in the corners of the columns.

Dynamics and Thermodynamics of the Mean Transpolar Drift and Ice Thickness in the Arctic Ocean

Abstract A theory for the mean ice thickness and the Transpolar Drift in the Arctic Ocean is developed. Asymptotic expansions of the ice momentum and thickness equations are used to derive analytic expressions for the leading-order ice thickness and velocity fields subject to wind stress forcing and heat loss to the atmosphere. The theory is most appropriate for the eastern and central Arctic, but not for the region of the Beaufort Gyre subject to anticyclonic wind stress curl. The scale analysis reveals two distinct regimes: a thin ice regime in the eastern Arctic and a thick ice regime in the western Arctic. In the eastern Arctic, the ice drift is controlled by a balance between wind and ocean drag, while the ice thickness is controlled by heat loss to the atmosphere. In contrast, in the western Arctic, the ice thickness is determined by a balance between wind and internal ice stress, while the drift is indirectly controlled by heat loss to the atmosphere. The southward flow toward Fram Strait is forced by the across-wind gradient in ice thickness. The basic predictions for ice thickness, heat loss, ice volume, and ice export from the theory compare well with an idealized, coupled ocean–ice numerical model over a wide range of parameter space. The theory indicates that increasing atmospheric temperatures or wind speed result in a decrease in maximum ice thickness and ice volume. Increasing temperatures also result in a decrease in heat loss to the atmosphere and ice export through Fram Strait, while increasing winds drive increased heat loss and ice export.

ENERGY EFFICIENT SOLUTIONS FOR SMALL CAPACITY ELECTRIC ARC FURNACES OF A FOUNDRY CLASS

The low specific power of the transformer in combination with the increased heat losses due to the geometrical factor and the unstable operation with long downtimes are predetermined by low technical and economic indicators of production, in comparison with the EAF of the "big" metallurgy. An urgent task is to search for low-cost methods to increase the energy efficiency of furnaces of this class by simulating the thermal work of the elements of the working space. Numerical simulation of heat transfer in the working space of foundry class AC EAF with a capacity of 3 tons has shown that with a duration of furnace downtime of 18–20 hours or more, replacing 40% of the walls lining and 16-20% of the roof lining by water cooled elements with a volumetric structure accumulating the skull, with using of “deep" bath with a reduced by 14–15% diameter of the radiating surface allows, at a given melting mass, to reach the energy consumption level of the furnace with a fully refractory lining and lower with a significant saving of refractories. Preloading scrap into the furnace in downtime increases energy efficiency, all other things being equal.

Rain exacerbates cold and metabolic strain during high-intensity running.

Outdoor exercise often proceeds in rainy conditions. However, there are very few studies reporting the physiological effects of cold with rain or wet-cold exposure on humans during exercise. The purpose of this study was to investigate the effects of rain on physiological responses during running exercise at 80% V̇Omax in the cold. Twelve healthy men (age: 21.7±3.3 years; height: 1.760±0.085 m; body weight: 68.8±7.1 kg; maximal oxygen consumption: 67.3±5.00 mL/kg/min) exercised on a treadmill at 80% V̇Omax intensity for 60 minutes with rain (RAIN) or not (CON) at 5 °C. Rectal temperature was significantly lower in RAIN than in CON at 10, 40, 50, and 60 minutes (P<0.05). Mean weighted skin temperature was significantly lower in RAIN than in CON during exercise (P<0.05). Oxygen consumption and rating of perceived exertion were significantly higher in RAIN than in CON at 50 and 60 minutes (P<0.05). Plasma lactate was significantly higher in RAIN than in CON at 10 minutes and from 40 to 60 minutes (P<0.05). Plasma norepinephrine levels were significantly higher in RAIN than in CON at 10 minutes and from 40 to 60 minutes (P<0.05). These results suggest that rain increased heat loss during the early phase of exercise in the cold, then heat production increased and transiently suppressed cold stress. However, with time, body heat loss intensified due to increasing wet area, and then energy expenditure and plasma lactate increased due to cold stress. Therefore, rain may decrease exercise performance and affect sport safety.

Numerical Studies of Electromagnetic Processes in Segmented Heavy-Gage Current-Carrying Conductors

The resistance of heavy-gage current-carrying conductors to alternating current of industrial frequency increases due to the skin effect and proximity effect, which leads to increasing heat loss during transmission of electrical energy. When power cables for a voltage of 110 kV or more are fabricated, segmented Milliken-type current-carrying conductors are used, which make it possible to reduce the resistance to alternating current. The objective of this work is to carry out a numerical study of electromagnetic processes in heavy-gage Milliken-type current-carrying conductors using mathematical simulation. For this purpose, a geometric model is constructed that takes into account the complex spatial structure of current-carrying conductors. For comparison, a geometric model is considered in which the wires are arranged parallel to each other. The electromagnetic processes in the current-carrying conductors are described by differential equations for the complex amplitude of vector magnetic potential derived from Maxwell’s equations. The proposed set of differential equations is supplemented with corresponding boundary conditions. The given problem was solved numerically on the basis of the ANSYS Maxwell software package constructed based on the finite element method. As a result of calculations, the fields of vector magnetic potential in the whole volume under study and the distributions of the current density vector in conductors were obtained, from which the resistances of current-carrying conductors as a whole and of each wire separately were calculated. The calculation results revealed that using Milliken-type current-carrying conductors makes it possible to reduce the conductor resistance by equalizing the current density distribution over the cross sections of wires when a segment of them is twisted.

WALLING THERMAL PROPERTIES INFLUENCED BY HEAT-STRESSED ELEMENTS IN EXTERNAL CORNER AREA

It is known that heat-stressed elements greatly affect the thermal properties of walling and contribute to the heat losses of a building. Heat-stressed elements decrease the temperature on the inner walling surface adjacent to the external corners. In addition to increasing heat losses, heat-stressed elements increase the condensation on the inner walling surface leading to mold appearance. This is one of the reasons that shows that the modeling of heat-stressed elements is a very important design stage. The article discusses the effect from these elements on thermal properties of multilayer walling in the external corner of a building. Using the ANSYS software package, the influence of heat-stressed elements on the heat transfer processes is modeled in the external corner area. A quantitative assessment of the thermal state of typical walling fragments under extreme heat-transfer conditions is given. The obtained research results can be used to increase the temperature in the area of heat-stressed elements and reduce their negative impact.

Sodium receiver designs for integration with high temperature power cycles

A variety of tube materials and geometries are considered in an analysis that identifies suitable sodium receiver designs for integration with next-generation thermodynamic power cycles. Sodium is capable of delivering outlet temperatures of >750∘C, however the net power output diminishes with rising temperatures due to tube material limitations on allowable flux density and increasing heat losses. Small tube diameters facilitate large thermal efficiencies and heat fluxes for all materials, however a large pressure drop penalty can somewhat mitigate these advantages. Traditional heat exchanger alloys perform quite poorly in comparison to Inconel 617 and Haynes 230, with allowable heat flux decreasing significantly as temperatures are increased beyond 600∘C. Multi-pass concepts offer greater control of flow-path exposure to the heat flux boundary condition than straightforward single-pass designs. A triple-panel design with small diameter Inconel 617 tubes balances thermal, hydraulic, and mechanical performance most effectively across all temperatures. For all candidate materials, sodium can augment power plant efficiency when integrated with a high temperature cycle (>600∘C). A combined receiver and power cycle efficiency percentage point improvement of 1.5% is possible using Ni-based superalloys at ∼650−700∘C compared to a baseline outlet temperature of 550∘C, resulting in a solar-to-electric power output increase of over 4%.

Analysis of a rotary passive heat recovery device for natural ventilation windcatcher

Based on the design of traditional architecture, windcatchers are devices which provides passive ventilation by manipulating pressure differentials around buildings induced by the movement of wind and difference in temperature. In temperature climates, it is effective in providing passive cooling during summer months. However, during winter months, the low air temperature supplied to the space can cause further thermal discomfort and increase heat loss which lead to higher energy consumption. This limits the capabilities of windcatchers to provide ventilation all year round. To address this issue, the present study proposes incorporating a rotary thermal heat recovery device into the windcatcher channel and investigate its performance using numerical modelling and experimental tests. The study focused on characterizing the design and performance of the copper radial blades of the proposed heat recovery device. The predicted results of the airflow and temperature showed good agreement with the experimental tests. Two types of radial blade designs were assessed in terms of the airflow velocity and distribution, the pressure drop and the heat recovery performance.

Body temperature responses of Great Tits Parus major to handling in the cold

Animals typically respond to stressful stimuli such as handling by increasing core body temperature. However, small birds in cold environments have been found to decrease body temperature (Tb) when handled over longer periods, although there are no data extending beyond the actual handling event in such birds. We therefore measured both the initial Tb decrease during ringing and standardized Tb sampling, and subsequent recovery of Tb after this handling protocol in wild Great Tits Parus major roosting in nestboxes in winter. Birds reduced their Tb by 2.3 °C during c. 4 min of handling. When birds were returned to their nestboxes after handling, Tb decreased by a further 1.9 °C over c. 2 min, reaching a Tb of 34.6 °C before taking 20 min to rewarm to 2.5 °C above their initial Tb. The Tb reduction during handling could be a consequence of increased heat loss rate from disrupted plumage insulation, whereas Tb reduction after handling might reflect reduced heat production. These are important factors to consider when handling small birds in the cold.

Infrared Thermography as an Indicator of Heat Loss in Fur-Chewing Chinchillas (Chinchilla Lanigera)

ABSTRACT Fur-chewing is a common problem in chinchilla (Chinchilla lanigera). It may affect the welfare of animals due to heat loss, thereby possibly impacting food and water intake to maintain body temperature. In this context, infrared thermography seems to be a suitable method of measuring heat emissions from the surface of objects. Sexually mature male domestic chinchillas were divided into two groups: “non-fur chewers”, exhibiting normal behaviour (n = 25), and “fur chewers” displaying fur-chewing behaviour (n = 23). Food and water intake (mean ± SD) measured in the control animals amounted to 20.7 ± 4.52 g and 15.9 ± 3.45 mL, while in fur-chewing chinchillas were 25% and 33% higher, respectively. Metabolic energy intake, were calculated 2.2 and 2.8 W for the control and fur-chewing animals, respectively. Heat flux through chewed areas was 6.06 mW cm-2, which is 2.8 times higher than through undamaged chinchilla fur. To sum up, thermal imagingexplicitly shows that fur-chewing causes increased heat loss. Disturbances in the maintenance of thermal homeostasis may be an additional factor that reduces the welfare of these animals.

Energy efficiency for cooling buildings in hot and dry regions using sol-air temperature and ground temperature effects

PurposeIn hot and dry climates, air conditioning accounts for a large portion of total energy consumption; therefore, this paper aims to investigate the impact of sol-air temperature and ground temperature on the loss of cooling energy in hot and dry regions of Iran.Design/methodology/approachIn line with this objective, the values of sol-air temperature along different directions and ground temperature at different depths were assessed with respect to climatic data of Yazd City. The impact of sol-air temperature and ground temperature on the rate of heat loss was investigated. So, energy loss of the walls aligned to four primary directions was calculated. This process was repeated for a 36 m2 building with three different shape factors. All analyses were conducted for the period from May to September, during which buildings need to be cooled by air conditioners.FindingsNumerical analyses conducted for hot and dry climate show that sol-air temperature leads to a 41-17 per cent increase in the wall’s energy loss compared with ambient temperature. Meanwhile, building the wall below the surface leads to a significant reduction in energy loss. For example, building the wall 400 cm below the surface leads to about 74.8-79.2 per cent energy saving compared with above ground design. The results also show that increasing the direct contact between soil and building envelope decreases the energy loss, so energy loss of a building that is built 400 cm below the surface is 53.7-55.3 per cent lower than that of a building built above the surface.Originality/valueThe impact of sol-air temperature and ground temperature on the cooling energy loss of a building in hot and dry climate was investigated. Numerical analysis shows that solar radiation increases heat loss from building envelope. Soil temperature fluctuations decrease with depth. Heat loss from building envelope in an underground building is lower than that from building envelope in a building built above the ground. Three different shape factors showed that sol-air temperature has the maximum impact on square-shaped plan and minimal impact on buildings with east-west orientation.

Methodology for partial vacuum pressure and heat losses analysis of parabolic troughs receivers by infrared radiometry

Loss of vacuum due to incoming gases (hydrogen or air) in evacuated receiver tubes of parabolic-through solar collectors (PTC) is one of the most common failures in large solar power plants and it has a significant impact on the thermal performance of the solar field. The loss of vacuum is translated in increasing heat losses and at certain point, damaged receivers must be replaced, but first they must be identified among all receiver pipes installed in a large solar field, which counts thousands units. Several efforts have been done to develop a methodology to locate receivers which loss completely the vacuum. These methodologies are based on the glass envelope temperature, the so called surface temperature method. In this work, the surface temperature method has been extended to determine partial vacuum pressure of receiver tubes not completely damaged and to determine its influence in their thermal performance. Results obtained using air as the incoming gas demonstrate that the methodology presented allows distinguishing partial vacuum pressure among 10−4, 10−2, 100, 102, 103 mbar in the receiver cover annulus but it does require accurate measurements that must be carefully addressed as described in this work. Further tests with this methodology may be also applied to determine the partial vacuum pressure of hydrogen in the annulus of this type of solar receivers.

The The Occurrence of Thermal Bridges in Hemp-Lime Construction Junctions

Thermal bridges increase heat losses in buildings and reduce the temperature of the internal envelope surface, causing moisture condensation and mould growth. This is an important issue for building materials based on organic components such as a hemp-lime composite, as they are particularly susceptible to biological degradation.The hemp-lime composite is used as a filling in timber frame construction. The increased cross-section of wooden elements together with the geometry change in the construction joints can form thermal bridges. The paper presents numerical analyses of temperature distribution in the area of construction elements connections, taking into account several variants of junctions: external walls, corners, and window placement in a wall. The thermal parameters of hemp-lime composites used in the analyses were obtained from the authors’ own research.Despite relatively good insulating properties, timber elements have a noticeable influence on the local increase of the heat transfer in hemp-lime composite structures, forming thermal bridges in the partitions themselves and in the construction nodes. However, the linear thermal transmittance coefficients in the presented joints were not very significant (in the range of 0.026 ÷ 0.092 W/(m·K) depending on the type of connection), proving the usefulness of this type of construction in energy-efficient buildings.

Instantaneous field measurements of thermal bridge parameters in ground floor residential room

The “thermal bridges” are defined as an isolated building’s areas, where the construction elements have higher thermal conductivity, compared with the rest of the building envelope. Thus, at cold winter conditions, a significant temperature difference may occur between neighbouring solid and air volumes within the construction. Moreover, it has been documented, that the heating energy demand of a building may be increased with more than 30%, due to the existence of thermal bridges and the increased heat losses from the indoors. Consequently, in the recent years, norms and standards have been developed, for avoiding thermal bridges during the building design process. But still, thermal bridges exist in the indoor environment, especially in older buildings, where no energy efficient measures have been applied. That is why, the presented study focuses on instantaneous field measurements of thermal bridge parameters in real existing ground floor residential room. The thermal bridge propagation is analysed relative to the indoor and outdoor air temperature and relative humidity, as well as with infrared thermal images of the affected external walls. The achieved results give valuable information about the generic conditions for thermal bridge existence, without considering the building envelope properties.

Analysis of the temperature distribution in the place of fixing the ventilated facade

Designers more and more often choose facade systems with ventilated layers for external walls, especially in the case of new buildings. They are also used to modernize existing buildings. Mechanical connectors are a characteristic element of these constructions. Often, they are ignored in calculating the heat balance of rooms and the entire building. Because they pierce the thermal insulation layer they cause point thermal bridges. The influence of thermal point bridges, usually made of aluminum, i.e. a material with very high thermal conductivity, for heat transfer turns out to be significant. Such thermal bridges significantly increase heat losses through building partitions. This situation increases the heat demand in the rooms to compensate for the heat loss. The article presents the results of the analysis of the impact of mechanical fasteners in ventilated facade systems on heat transfer in the building envelope. The influence of various materials and constructional solutions on the thermal conditions in these walls was investigated.

ENERGY EFFICIENCY OF LIFE PROTECTION OF SYSTEMS FOR RAILWAY VEHICLES

Passenger cars consume a fairly significant share of electricity to create comfortable conditions, when transporting passengers. The conducted studies of energy efficiency improvement taking into account the results of mathematical modeling of thermal processes it was established that during the design of passenger cars designers do not take into account a number of factors, affecting energy efficiency life support systems for passenger cars. In the calculations of the thermal balance of the car only heat is taken into account, supplied by heating pipes for more accurate calculations thermal balance of a passenger car the given heat must be taken into account in the thermal balance of the car. Experimental measurements confirmed presence zones of temperature fields with different temperature modes, separated by a decorative ceiling in which the zone of constructive ceiling cavity overheats over the normative indicators. This leads to increased heat loss through the roof of the carriage. In particular, it has been established that the proposed modernization on increasing the energy efficiency of the heating system can be implemented at relatively low cost, in the conditions of existing carriages depot, which will reduce energy consumption for heating 13.4% or UAH 25.9 million for a year. Improved mathematical model non-stationary thermal regime of a passenger car allows comprehensive analysis thermal processes of a passenger car, taking into account its constructive changes by mathematical experiment. Thus, this study will allow not only to increase energy efficiency but also provides grounds for reducing the power of the heating system by at least 10%, which will reduce the metal content of the heating system and, as a consequence of the reduction of the wagon's packaging, reduction of power of electric devices, wires, and the number of electrically heated TENs will decrease.