Average Heat Load Research Articles

Heat transfer and rock-soil temperature distribution characteristics in whole life cycle for different structure sizes of medium-deep U-shaped butted well

Medium-deep U-shaped butted well (MUBW) is one of the most potential geothermal-heating way. However, the thermal interference may happen during long-term geothermal extraction period, which results in a heating performance attenuation. In this work, the heat transfer performance and surrounding rock-soil temperature distribution characteristics of MUBW in whole life cycle were investigated. The three-dimension full-size heat transfer model for long-term thermal extraction was proposed and the different structure sizes were considered. The results showed that the thermal interference is more likely to happen in a high heating load condition for the conventional structure size. By increasing horizontal length from 200 m to 600 m, the average specific heating load could increase by 26.1 %. When vertical depth increases to 3000 m, the heating load increases by 47.0 % at least. It is noted that the annual average inlet and outlet temperatures decrease by 5.1 °C in the whole life cycle, which should be considered in design on system operation. Additionally, the horizontal length of 600 m is large enough to avoid thermal interference in whole life cycle for MUBW with depth of 2000∼3000 m. This study has a practical meaning for ensuring a sustainable thermal extraction of MUBW.

Thermal-hydraulic and structural analyses of an additive manufactured panel mock-up for Wendelstein7-X

After the successful short pulse operation phase 1 (OP1) of the stellarator Wendelstein 7-X with maximal plasma energies of 200 MJ, the upcoming long pulse OP2 aims at stepwise higher energies up to 18 GJ. A series of the stainless steel wall protection panels is positioned behind the divertor pumping gaps for average stationary heat loads of 100 kW/m². These panels were produced by electron beam welding of stainless steel parts to build the housing of the cooling channels. This technology was more demanding than foreseen due the complicated 3D weld seams required by the shaping of the panels. An innovative technology which is more adapted to the panel geometry is additive manufacturing. It intends to bring significant advantages by printing the housing as a single piece without welds.The paper introduces the thermal-hydraulic and structural analyses of an additive manufactured panel mock-up performed with ANSYS V2022R2. The purpose of the calculation is to compare the thermal, hydraulic and structural performance of the improved design based on additive manufacturing and the present one. The welding process dictated the design of the cooling channel that induced local recirculation areas, additional local pressure drops, non well cooled areas for weld seams integration. In addition the weld strength assessment required special codes and methods, which cost more time and efforts. Without these constraints, additive manufacturing offers the opportunity of more freedom for the design of the cooling channel to reach better heat transfer performance of the panel.

Investigating the relationship between heat load and shade seeking behaviour in dairy buffaloes.

The study presented in this Research Communication aimed to investigate the relationship between physiological responses, body surface temperature and shade-seeking behaviour in Nili Ravi dairy buffaloes during summer months. We enrolled 60 buffaloes, and each animal was observed for three consecutive days starting before sunrise until they moved towards the shade structures. A repeated measures ANOVA was employed to assess the changes in physiological parameters and body surface temperature between the early morning and the occurrence of shade-seeking behaviour. The average temperature humidity index and heat load index during the behavioural monitoring period (0400 to 1200 h) were 81.3 ± 6.5 and 92.9 ± 17, respectively (mean ± sd). There was no significant difference in core body temperature between sunrise and the time of shade-seeking event. However, the buffaloes had a slightly higher respiration rate at the time of shade-seeking (19.2 vs. 22.4 breaths/min). In addition, body surface temperature, measured at the flank region, shoulder, base of the ear and forehead was significantly higher at the occurrence of shade-seeking behaviour compared to the early morning. On average, the buffaloes sought shade when the surface temperature was 2°C higher than the temperature recorded before sunrise. Overall, the current findings suggest that body surface temperature, rather than core body temperature was strongly associated with shade-seeking behaviour in dairy buffaloes. These findings could be useful in developing strategies to mitigate the effects of heat stress in dairy buffalo herds and thereby improve animal welfare.

Unsteady conjugate heat transfer simulation of wall heat loads for rotating detonation combustor

Rotating detonation engines (RDEs) are the most promising pressure-gain combustion devices, but their long-duration operations are hindered by the harsh thermal environment inside the chamber. This study analyzes the instantaneous and average heat loads on chamber walls of RDEs based on the newly developed unsteady conjugate heat transfer (CHT) OpenFOAM solver named multiRegionBYRFoam. To enhance accuracy in predicting heat transfer characteristics compared to decoupled simulations focusing solely on fluid or solid behavior, three-dimensional CHT simulations are conducted for a premixed H2/air annular RDE coupling the detonation simulation with heat conduction in both inner and outer chamber walls. The transient time evolutions of wall heat flux in RDEs are numerically captured for the first time and agree well with experiments. The calculated peak wall heat flux is 1.98 MW/m2 at the inner wall and 2.63 MW/m2 at the outer wall when a single detonation wave propagates with a mass flow rate of 0.227 kg/s. By investigating the influence of inlet flow conditions and detonation modes, valuable guidelines on designing efficient thermal management systems for RDEs are obtained: larger mass flow rates and multi-wave modes result in higher average wall heat flux; the heat flux at the outer wall exceeds that at the inner wall while both walls require effective cooling for gas turbine engines with a rotating detonation combustor. Furthermore, a novel heat transfer model for RDEs is proposed based on a thermal operation map depicting total heat transfer rates to describe the nonlinear impact of mass flow rate and number of detonation waves, which can be employed to predict total wall heat loads under specific operation conditions of RDE.

Effect of typical low-impact development measures on control of thermal loads from urban stormwater runoff

Ground hardening in urban areas increases the risk of thermal enrichment in surface rainwater runoff. Moreover, the thermal pollution from rainwater runoff has become an important problem that damages the urban aquatic environment. Current studies have focused mainly on the potential hazard caused by runoff thermal pollution to aquatic microorganisms. However, there are few studies on the efficacy of controlling runoff thermal load through low-impact development (LID) and renovation in urban areas. The effects of LID modification were evaluated by monitoring the characteristics of the runoff thermal load on each underlying surface in the study area and conducting laboratory-scale bioretention experiments. The results showed that the initial thermal effect of each underlying surface was significant after the start of rainfall, based on the thermal load. Ceramic granules are remarkable bioretention fillers. Their average heat load and volume reduction rates are 55.6 % and 32.7 %, respectively. After LID modification, the thermal load of surface runoff in the study area decreased to 73.42 % under similar rainfall conditions. After the secondary treatment of the bioretention facility, the total thermal load of the outflow facility was 31.40 % of that before renovation. The peak thermal load reduced by 69.15 % and was delayed for 10 min. The control effect differed statistically.

Perhitungan Daya Kompresor dan Beban Kalor Pada Hasil Tangkapan Ikan Laut

A refrigeration machine is needed on a fishing boat because the purpose of catching is to catch as many fish as possible and maintain the quality of the catch. In general, fishing vessels use mechanical refrigeration machines in an effort to maintain the quality of the catch up to the hands of consumers. The results of checking products that enter the hold showed the average initial temperature of the fish entering the hold was 11,7 oC. The final temperature of fish products after going through the freezing process is 2,075 oC. The total product load calculation is 101,1 KW and the average product heat load on the hold is 9,1 KJ/s. By knowing the suction pressure, exhaust, and working temperature of the compressor through a worksheet that is journalized every day, as well as the temperature in the pipe after the condenser, and the expansion valve using the Mollier R-22 diagram and the Saturation Properties-Temperature R-22 table, it is known that the average compressor power average of 1,9 KW and actual COP averaging is 4,6 KJ/Kg. The total compressor power result calculation is 20,96 KW with an average usage of 1,9 KW. The total result of the COP actual calculation is 51,4 with an average of 4,6.

Thermodynamic study of a novel combined heat and power system integrated with solar energy

Combined heat and power systems crucially require high efficiency and flexibility because of the high penetration level of intermittent renewable power. The efficiency and flexibility of traditional combined heat and power systems are limited by their heating-controlled operation mode. Therefore, a heat-power decoupling technique with high energy utilization efficiency and flexibility is necessary. In this study, a novel combined heat and power system integrated with solar energy is proposed. Detailed analytical models based on thermodynamics laws are developed, and a 330 MW unit is used as an example to assess the comprehensive thermodynamic performance and operational flexibility of the proposed system. Results show that the average net energy efficiency of the novel system during daytime and nighttime can reach 54.68% and 55.75%, respectively. Meanwhile, the average net exergy efficiency of the novel system during daytime and nighttime can reach 38.73% and 38.83%, i.e., an improvement of 2.43 and 2.59 percentage points, respectively, compared with the traditional combined heat and power system. The peak-shaving ability of 97.80 MW can be improved, and 295.35 tons of standard coal per day can be saved using the novel system compared with the traditional combined heat and power system under the average rated heating load. This study provides a promising approach for utilizing solar energy to enhance the efficiency and flexibility of combined heat and power plants.

Experimental study on sorption–desorption characteristics of natural composite desiccant with metal embedment

The present study investigates the effect on total moisture sorption, moisture sorption rate, moisture desorption rate, and reduction in the temperature of dehumidified air of metal-embedded natural composite desiccants (MENCDs), which can be used in dehumidification systems. A natural composite desiccant, in which the unutilized portion of the spherical desiccant material is replaced with a metallic ball, is proposed. Stainless steel balls with a diameter of 4.75 and 6.35 mm are used to make different thickness ratios (TR = 1, 0.525, and 0.365) of MENCDs. The natural composite desiccant is prepared from dried cow dung and polyvinyl pyrrolidone with a ratio of 3:1. Experiments are conducted to find the optimum thickness ratio of MENCDs. The total moisture sorption, moisture sorption rate, total heat load reduction, and exergy efficiency of these dehumidification systems are investigated under different relative humidities (RH = 65% to 85%), and at a constant temperature and velocity. Desorption characteristics are tested under 328 K and 5% RH. The total moisture sorption of MENCDs with a TR of 0.365 is found to be 11.84 g/100 g, which is 17% higher compared to natural composite desiccants (i.e., TR = 1) at 85% RH, whereas, the total moisture sorption rate is 0.4 g/100 g⋅min, which is 20.57% higher for TR of 0.365 compared to TR = 1. Moisture desorption rate for TR = 0.365 is 16.66% higher compared to TR = 1. The average exergy efficiency of these systems is 60%. The average exergy efficiency of these composite desiccants with a TR = 0.365 is 9.6% higher compared to TR = 1. The average total heat load reduction for composite desiccants with a TR = 0.365 is 24% higher compared to TR = 1. The experimental study shows that the MENCDs will help to increase total heat load reduction, sorption and desorption rate, and total moisture sorption of dehumidified air with optimum thickness ratio for enhanced utilization of a composite desiccant for dehumidification systems.

Heat transfer to proximal cylinders in hypersonic flow

Uncontrolled atmospheric entry of meteors, satellites, and spacecraft components often leads to their partial or complete demise. In this destructive process, driven by hypersonic ablation, reentry objects fragment, interact, and alter each other's aerothermal environment. The effect of these interactions on the heat transfer to the fragments has not been investigated, despite the heat transfer's importance in hypersonic ablation and reentry demise. This study focuses on the numerical investigation of heat transfer to proximal circular cylinders in a thermochemically frozen flow and in two dimensions. First, binary body configurations at Mach numbers 2, 4, and 8 revealed that the heat load and peak heat transfer can be augmented for either or both proximal bodies by +20% to −90% of an isolated body. Second, different clusters of five proximal bodies showed that the heat load to any given body can range from +40% to −90% of an isolated body. Moreover, the average heat load in a cluster is found to vary between +20% and −60% of an isolated body. Intuitively, clusters which are thin in the direction perpendicular to free-stream velocity and long in the direction parallel to the free-stream velocity have their cluster-averaged heat load reduced. In contrast, thick and thin clusters, in directions perpendicular and parallel to the free-stream velocity, are subject to an increased cluster-averaged heat load.

Curve Optimization for the Anidolic Daylight System Counterbalancing Energy Saving, Indoor Visual and Thermal Comfort for Sydney Dwellings

Daylight penetration significantly affects building thermal-daylighting performance, and serve a dual function of permitting sunlight and creating a pleasant indoor environment. More recent attention has focused on the provision of daylight in the rear part of indoor spaces in designing sustainable buildings. Passive Anidolic Daylighting Systems (ADS) are effective tools for daylight collection and redistribution of sunlight towards the back of the room. As affordable and low-maintenance systems, they can provide indoor daylight and alleviate the problem of daylight over-provision near the window and under-provision in the rear part of the room. Much of the current literature on the ADS pays particular attention to visual comfort and rarely to thermal comfort. Therefore, a reasonable compromise between visual and thermal comfort as well as energy consumption becomes the main issue for energy-optimized aperture design in the tropics and subtropics, in cities such as Sydney, Australia. The objective of the current study was to devise a system that could act as a double-performance of shade and reflective tool. The central aim of this paper is to find the optimum curve that can optimize daylight admission without an expensive active tracking system. A combination of in-detail simulation (considering every possible sky condition throughout a year) and multi-objective optimization (considering indoor visual and thermal comfort as well as the view to the outside), which was validated by field measurement, resulted in the optimum ADS for the local dwellings in Sydney, Australia. An approximate 62% increase in Daylight Factor, 5% decrease in yearly average heating load, 17% savings in annual artificial lighting energy, and 30% decrease in Predicted Percentage Dissatisfied (PPD) were achieved through optimizing the ADS curve.

Superstructures of water-dispersive hydrophobic nanocrystals: specific properties.

Here, we describe water-soluble superstructures of hydrophobic nanocrystals that have been developed in recent years. We will also report on some of their properties which are still in their infancy. One of these structures, called "cluster structures", consists of hydrophobic 3D superlattices of Co or Au nanocrystals, covered with organic molecules acting like parachutes. The magnetic properties of Co "cluster structures" a retained when the superstructures is dispersed in aqueous solution. With Au "cluster structures", the longer wavelength optical scattered spectra are very broad and red-shifted, while at shorter wavelengths the localized surface plasmonic resonance of the scattered nanocrystals is retained. Moreover, the maximum of the long-wavelength signal spectra is linearly dependent on the increase in assembly size. The second superstructure was based on liquid-liquid instabilities favoring the formation of Fe3O4 nanocrystal shells (colloidosomes) filled or unfilled with Au 3D superlattices and also spherical solid crystal structures are called supraballs. Colloidosomes and supraballs in contact with cancer cells increase the density of nanocrystals in lysosomes and near the lysosomal membrane. Importantly, the structure of their organization is maintained in lysosomes for up to 8 days after internalization, while the initially dispersed hydrophilic nanocrystals are randomly aggregated. These two structures act as nanoheaters. Indeed, due to the dilution of the metallic phase, the penetration depth of visible light is much greater than that of homogeneous metallic nanoparticles of similar size. This allows for a high average heat load overall. Thus, the organic matrix acts as an internal reservoir for efficient energy accumulation within a few hundred picoseconds. A similar behavior was observed with colloidosomes, supraballs and "egg" structures, making these superstructures universal nanoheaters, and the same behavior is not observed when they are not dispersed in water (dried and deposited on a substrate). Note that colloidosomes and supraballs trigger local photothermal damage inaccessible to isolated nanocrystals and not predicted by global temperature measurements.

The combined effect of water management and environmental control on the planting of two varieties of garden egg in a partially shaded greenhouse: an energy and yield indicator analysis

The objective of this study is to investigate the performance of partially shaded solar greenhouse and water management on the growth and bioactive yield of garden eggs under micro climate management. For this reason, two local varieties of garden egg (Solanum aethiopicum and Solanum gilo) were planted in a partially shaded natural convention greenhouse at Umudike South Eastern Nigeria and nurtured for four months from June to September before harvest. The plants were supplied water at 50, 70 and 100% field capacity with the internal condition of the greenhouse naturally controlled by the ambient condition. The evaluation parameters were the average monthly heat load flux, ventilation flux, transpiration rate, plant growth parameters, and phytochemicals and anti-oxidants characteristics of the fruits from the garden egg in comparison with the open field plantation. Thermal analysis showed that an increase in temperature and lower relative humidity increases the evapotranspiration rate in the greenhouse. The average sensible and latent heat load ranged from 10.9 to 121.3 W/m2 and 21.94 to 63.56 W/m2 respectively. In contrast, the average monthly ventilation flux which was deduced as a function of heat load ranged from 5.307 × 10−3 to 8.053 × 10−3 m3/m2.s. While water management and greenhouse had negative effects on most of the growth parameters of the garden egg, they significantly increased the antioxidant contents in the garden egg, particularly total phenolic contents (TPC) and total flavonoid contents of fruits which is a quality needed for a healthy body. This shows that climatic control and water management influence garden egg quality more than the growth parameters. The data from this study will enhance understanding of the influence of water stress on garden egg yield under controlled environmental conditions, which might be important in providing the needed nutrient for healthy body.

Generation and verification of vertical meteorological data for building energy simulation from a 325-meter Beijing meteorological tower

As the number of high-rise buildings increases, so does the demand for meteorological data at different heights. The difference in meteorological elements in the vertical direction should be considered in heating, ventilation, and air conditioning design and building performance simulations (BPS). This study uses a meteorological tower in Beijing as a model to provide a reduced-order method for data of typical meteorological years (TMY) and outdoor air design condition for high-rise buildings. The vertically-translated TMY results obtained by this method could achieve load simulation results close to the average load level of the observed station meteorological data. The difference between the cumulative heat load obtained from vertically-translated TMY data and the average cumulative heat load obtained from observed station meteorological data was 0.82–6.08%. By verifying the vertically-translated data, we observed that the vertically-translated outdoor air design condition at different altitudes were consistent with the direct statistical results based on observation data. This reduced-order method is helpful for modifying energy consumption simulations and the energy-saving designs of high-rise buildings.

Evaluation of the impact of input uncertainty on urban building energy simulations using uncertainty and sensitivity analysis

The energy consumption of cities is increasing fast due to growing global population and rapid urbanization. Urban Building Energy Models (UBEMs) are promising tools to simulate the energy demand of buildings under different urban scenarios. Nowadays, the major barriers to the effective use of UBEMs are the uncertainty related to their input parameters and the lack of good-quality, open energy consumption data. The latter make deterministic UBEM simulations unreliable, and calibration approaches unsuitable for most cities in the world. The present work proposes to combine physics-based UBEMs with Uncertainty and Sensitivity Analysis on the main input parameters using aggregated data on energy use from regional/national statistics. The proposed procedure selects the most influential input parameters and characterizes their uncertainty through Forward Uncertainty Analysis and Sensitivity Analysis to obtain stochastic load profiles for space heating and cooling. The method was first tested against hourly thermal power profiles metered on a heterogeneous sample of buildings in Verona (Italy). The average heating load profile obtained is significantly improved compared to deterministic, archetype-based simulations in terms of energy needs and peak loads. The overestimation of residential buildings peak load is reduced from 80% to 25%, and the deviation in the energy needs calculation drops from 18% to 10%. The proposed simulation procedure was then applied to a district of Milan (Italy), including more than 600 buildings, resulting in similar variations. Overall, the results demonstrate that considering the uncertainty of operational, geometrical and physical parameters is of the utmost importance to obtain reliable urban simulations.

Design optimization of the solar heating system for office buildings based on life cycle cost in Qinghai-Tibet plateau of China

The Qinghai-Tibet Plateau is rich in solar energy resources (SER), and the operation conditions of office buildings are consistent with the daily fluctuations in solar radiation. Solar heating for office buildings on the plateau has great potential. To obtain the optimal capacity ratio of solar heating system (SHS) for office buildings in plateau area, an optimization model of SHS capacity matching was established. The minimum life cycle cost (LCC) was taken as the objective function, and collector area, tank volume and auxiliary heat source (AHS) power as the decision variables in the model. The Qinghai-Tibet plateau was divided into five typical regions, and optimization was carried out for each region. The results show that the system LCC optimized by the intermittent heating load is 12% lower than that calculated by the average intermittent heating load and 44% lower than that calculated by the average parameter method for Lhasa. From an economic perspective, the AHS is suitable for electric boilers or gas boilers in regions with rich or general SER and cold regions with abundant SER. The AHS is suitable for electric boilers, air source heat pumps, or gas boilers in severely cold regions with abundant SER.

Analytical Study of a Solar Hybrid Air-conditioning System Assisted Solar Absorption Using R-410A for Refrigeration Applications

This research focuses on the design, modeling, and simulation of absorption solar air-conditioning systems. Key performance parameters are identified and optimized for maximum efficiency, and the system was simulated using climatic conditions in Thi-Qar, Iraq, providing a good trend for the system to meet domestic airconditioning needs, which has a direct effect on the angle of incidence of solar radiation. The results of solar collectors and their effective performance in saving energy and improving system efficiency were discussed, where the work was performed on a solar heater with an evacuated tube with an area of 1.8 m2. The rate of emitted solar radiation was equal to 1000 W/m2. The average heat load of the solar heater was provided at a rate of 0.190 kW to 1.291 kW. The experiment in this paper was conducted in two stages. First, the solar heater was connected in the first case before the compressor. The reported results showed an increase in energy savings with average heater temperatures rising to 25% to 55% of the total energy consumed in the cooling cycle per day. The gas was heated to temperatures ranging from 45 to 65◦C, while the cooling rate was constant at 3.43. Second, the solar heater was connected after the compressor in the second case. The solar heater provided a significant improvement in system performance factor with an average of 5.1 to 13 and energy amount ranging from 15% to 24% of the total energy consumed. It is noted that the cooling load improved from 3.43 to 5.54 kW. The rate of thermal heating in the second case was from 100 to 160◦C gradually. Finally, it is noted that the second case has a much greater service advantage and economic feasibility than the first, and the system has improved as a result of improving the amount of cooling load while reducing energy consumption and increasing the overall performance of the system factor resulting from the improvement of the special conditions of the coolant used in the (R-410a) cycle.

Analysis of indoor environment and insulation performance of residential house with double envelope vacuum insulation panels

Double envelope vacuum insulation panels (VIPs) have a possibility to significantly increase the service lifetime. In this paper, double envelope VIPs were produced and installed in the residential house. The performance of installed VIPs was evaluated by using the measuring data of heat flux meter. In addition, the total energy, the heating load and the indoor thermal environment of this house were measured and analysed. The average heating load and the average temperature difference between room temperature and ambient air temperature on the representative day was 2.49 kW and 29.9 oC, respectively. The heat loss coefficient per floor area was estimated as 0.69 W/(m2K) and it was almost the same as the value calculated at the time of design. The result of indoor environment measurement showed that the room temperature was maintained at around 20 oC and PMV was -0.5 oC or higher although the outside air temperature fluctuated between -5 oC and -10 oC. The effective thermal conductivities of double envelop VIPs were all estimated as 0.01 W/(mK) or less. It is considered that the insulation performance of the vacuum insulation panels is maintained.

Understanding detachment of the W7-X island divertor

The fundamental behavior of the W7-X island divertor under detached conditions, which has been theoretically predicted with the EMC3-Eirene code, is re-examined here under the experimental conditions achieved so far and compared with the first experimental results. Both simulations and experiments cover a range of divertor configurations and plasma parameters, and show the following common trends: (1) with rising impurity radiation, the target heat load decreases ‘uniformly’ over the entire target surface in the sense that both the peak and average heat loads can drop by an order of magnitude. Impurity radiation (mainly from intrinsic carbon) occurs primarily at the plasma edge and the resulting negative impact on the stored energy is less than 10%. (2) When the total radiation exceeds a critical level, the target particle flux (the recycling flux Γrecy) begins to fall and can drop by a factor of 3–5 at high radiation levels without an obvious indication of significant volume recombination. (3) While Γrecy decreases, the divertor neutral pressure continues to build up and reaches a maximum, at which point Γrecy has declined significantly. (4) During detachment, the electron temperature at the last closed flux surface falls in a way that is not quantitatively understandable from parallel classical heat conduction processes. This paper presents a physical explanation of the numerical/experimental results described above. Furthermore, using the EMC3-Eirene code as a diagnostic tool, we are able, apparently for the first time, to provide a full quantitative analysis of each transport channel in the island divertor, aiming to clarify how the island divertor plasma self-regulates to maintain particle, energy, and momentum balance under detached conditions.

Optimal Operation of Low-Capacity Heat Pump Systems for Residential Buildings through Thermal Energy Storage

The paper provides results from a hardware-in-the-loop experimental campaign on the operation of an air-source heat pump (HP) for heating a reference dwelling in Pisa, Italy. The system performances suffer from typical oversizing of heat emission devices and high water-supply temperature, resulting in HP inefficiencies, frequent on-off cycles, and relevant thermal losses on the hydronic loop. An experimentally validated HP model under different supply temperatures and part-load conditions is used to simulate the installation of a thermal storage between heat generator and emitters, in both series and parallel arrangements. Results relative to a typical residential apartment show that the presence of the thermal storage in series configuration ensures smoother heat pump operation and energy performance improvement. The number of daily on-off cycles can be reduced from 40 to 10, also saving one-third of electric energy with the same building loads. Preliminary guidelines are proposed for correctly sizing the tank in relation to the HP capacity and the average daily heating load of the building. A storage volume of about 70 L for each kilowatt of nominal heating capacity is suggested.

System design and experimental verification of an internal insulation panel system for large-scale cryogenic wind tunnel

With the rapid development of aerodynamics for high speed aircraft, the flight experiments need to be carried out under ultra-high Reynolds number condition to simulate actual high-speed flight conditions, which puts forward higher requirements for the wind tunnel. Reynolds number increases rapidly as the decrease of the flow temperature because the viscosity of the working gas decreases and the density increases. As a result, a pressurized tunnel at cryogenic temperature can provide real-flight Reynolds numbers. Therefore, cryogenic wind tunnel is one of the best testing facilities to rech ultra-high Reynolds number. The thermal insulation system is crucial for the design and operation of the cryogenic wind tunnel. In this paper, the features of an internal insulation system for the cryogenic wind tunnel are firstly highlighted in comparison with traditional insulation systems. The internal thermal insulation system for the cryogenic wind tunnel is discussed. In order to evaluate the thermal insulation performance, the heat transfer calculation for a typical wind tunnel region with the diameter of two meters is carried out using finite element method based on the analyses of the heat transfer conditions. The averaged heat load from the environment is obtained to optimize the liquid nitrogen consumption during the wind tunnel operation. The thickness of the panel should be 150 mm to reach the design target of averaged heat flux 60 W/m2. Meanwhile, the typical region is constructed according to the new internal insulation system. Cryogenic test is conducted and it is proven that the new internal insulation system could efficiently prevent the environment heat flow and ensure the normal operation of the cryogenic wind tunnel.