Total Thermal Load Research Articles

Type I ELM filament heat fluxes on the KSTAR main chamber wall

Heat loads deposited on the first wall by mitigated Type I ELMs are expected to be the dominant contributor to the total thermal plasma wall load of the International Thermonuclear Experimental Reactor (ITER), particularly in the upper main chamber regions during the baseline H-mode magnetic equilibrium, due to the fast radial convective heat propagation of ELM filaments before complete loss to the divertor. Specific Type I ELMing H-mode discharges have been performed with a lower single null magnetic geometry, where the outboard separatrix position is slowly (∼7s) scanned over a radial distance of 7cm, reducing the wall probe–separatrix distance to a minimum of ∼9cm, and allowing the ELM filament heat loss to the wall to be analyzed as a function of radial propagation distance. A fast reciprocating probe (FRP) head is separately held at fixed position toroidally close and 4.7cm radially in front of the wall probe. This FRP monitors the ELM ion fluxes, allowing an average filament radial propagation speed, found to be independent of ELM energy, of 80–100ms−1 to be extracted. Radial dependence of the peak filament wall parallel heat flux is observed to be exponential, with the decay length of λq, ELM ∼25 ± 4mm and with the heat flux of q∥, ELM= 0.05MWm−2 at the wall, corresponding to q∥ ∼ 7.5MWm−2 at the second separatrix. Along with the measured radial propagation speed and the calculated radial profile of the magnetic connection lengths across the SOL, these data could be utilized to analyze filament energy loss model for the future machines.

Analysis and validation of transient thermal model for automobile cabin

As automobile cabin thermal environment is complex and continually varies during its travel on road, a dynamical thermal load model based on response factor method has been presented in this paper. To shorten the calculating time, a fast-response thermal load calculation scheme has been proposed which has optimized iterative error, and the calculating time can be finally reduced to 0.95s when time step is 50s. To validate the reliability of this model, several tests have been carried out under ambient conditions. The tests results show that the interior temperature error is within 5% between simulated value and experimental data. Also the simulated conduction thermal load gained through cabin panels except bottom panel closely follows the heat conduction measured by HFM-215 which both value fluctuate around 900W. In addition, detailed analysis on how to reduce the thermal conduction load is put forward in this paper, which shows that cutting down thermal conductivity of envelopes will be the most effective method among thickness, thermal conductivity and special heat capacity of envelopes. Meanwhile, the influences of solar altitude to solar radiation thermal load, vehicle velocity to interior panel temperature, glazing transmissivity to solar radiation thermal load and total thermal load during the process of driving for a whole day have also been analyzed in detail in this paper.

Energy efficiency evaluation of hospital building office

One of the strategy employed in building design is reducing energy consumption while maintaining the best comfort zone in building indoor climate. The first step to improve office buildings energy performance by evaluating its existing energy usage using energy consumption intensity (Intensitas Konsumsi Energi, IKE) index. Energy evaluation of office building for hospital dr. Sayidiman at Kabupaten Magetan has been carried out in the initial investigation. The office building is operated with active cooling (air conditioning, AC) and use limited daylighting which consumes 14.61 kWh/m2/month. This IKE value is attributed into a slightly inefficient category. Further investigation was carried out by modeling and simulating thermal energy load and room lighting in every building zone using of Ecotect from Autodesk. Three scenarios of building energy and lighting retrofit have been performed simulating representing energy efficiency using cross ventilation, room openings, and passive cooling. The results of the numerical simulation indicate that the third scenario by employing additional windows, reflector media and skylight exhibit the best result and in accordance with SNI 03-6575-2001 lighting standard. Total thermal load of the existing building which includes fabric gains, indirect solar gains, direct solar gains, ventilation fans, internal gains, inter-zonal gains and cooling load were 162,145.40 kWh. Based on the three scenarios, the thermal load value (kWh) obtained was lowest achieved scenario 2 with the thermal value of 117,539.08 kWh.The final results are interpreted from the total energy emissions evaluated using the Ecotect software, the heating and cooling demand value and specific design of the windows are important factors to determine the energy efficiency of the buildings.

Effect of controlling airflow in a solar chimney on thermal load in a built environment

Purpose The purpose of this paper is to investigate a wall-integrated solar chimney for passive ventilation of a building cavity. Ventilation is required to improve the circulation of air in the built environment. This can be achieved through natural or forced convection. Natural circulation can be driven by renewable energy, and so it promotes sustainable exploitation of energy resources. Solar energy is one of the promising renewable energy resources. Design/methodology/approach The chimney was designed to face the Equator on the wall of a room which required ventilation. Mean monthly daily heating and cooling loads of the room were computed with and without a solar chimney by using hourly meteorological data from nine different weather sites at low, medium and high latitudes. The chimney was implemented with and without airflow control, and simulated by using the ESP-r software. Findings Results show that the solar chimney with airflow control marginally reduced the heating load in the building envelope, with a similar effect being exhibited by the chimney with uncontrolled airflow. The cooling load was reduced by the controlled airflow at all the nine sites. In contrast, the uncontrolled airflow increased the cooling load at some sites. In addition, the chimney with airflow control reduced the annual total thermal load at all the sites, while the chimney with uncontrolled airflow raised the total thermal load at some locations. Originality/value The performance of solar chimneys designed with and without airflow control systems has been investigated under the same prevailing meteorological conditions at a given site. Findings show that controlling airflow in a solar chimney reduces the total thermal load in the built environment. This information can be applied in different parts of the world.

Equivalent-homogeneous-layers-set method for time-dependent heat transfer through hollow-block walls

An equivalent-homogeneous-layer-set (EHLS) method to account for the time-dependent heat transfer through a wall composed by hollow-blocks is proposed. This method considers the two-dimensional heat transfer due to conduction through the solid frame, the heat transfer by natural convection inside the air-cavities, and the heat transfer by radiation between air-cavity surfaces. The EHLS method gives an equivalent wall, composed by a set of homogeneous layers, that has a similar thermal behavior than the original hollow-block wall. Convection and radiation inside the air-cavities are considered by using temperature dependent heat coefficients and a radiative correction factor. This radiative correction factor is calculated for different values of the in-cavity fractional area and different aspect ratios of the air-cavities by comparing numerical results of the EHLS method with results of an experimentally validated two-dimensional model, in steady-state. This experimentally validated two-dimensional model, for time-dependent periodic conditions, is used to validate the EHLS method. Differences are up to 3.4% for the energy transferred through the wall, and 7% for both the sol–air decrement factor and the lag-time when the hollow-block wall is in a non-air conditioned room and up to 6% for the total thermal load when it is in an air-conditioned room. The EHLS method can be implemented into whole-building simulations programs and can be extended for other constructive systems for walls or roofs that have air-cavities inside, using the appropriate convective and radiative coefficients and radiative correction factor.

Numerical and experimental study on heat transfer characteristic and thermal load of the freezer gasket in frost-free refrigerators

The present study has been carried out to analyze the heat transfer characteristics and thermal load near the freezer gasket region of a 649 L domestic frost-free refrigerator/freezer. Both 3D numerical simulations and experimental test were performed. The numerical models for different freezer gasket sections were developed, while considering the non-uniform distribution of temperature inside the freezer cabinet. The calculated temperatures showed acceptable agreement with the measured temperatures. The total thermal load of gasket region is 10.57/6.68 W, in the status of compressor on/off. Thermal load of cold-bridge accounts for 23.8%/25.8% of the total thermal load, and thermal load of gasket bulk holds 76.2%/74.2%, respectively. When the compressor on–off time ratio is 7:3, total thermal load near the freezer gasket region is 9.40 W during an on–off cycling operation of compressor, accounting for 17.1% of the total thermal load in the freezer cabinet.

Development of a retro-reflective material as building coating and evaluation on albedo of urban canyons and building heat loads

Retro-reflective materials (RRM) applied as building coatings are a possible means to help counter urban heat islands. In this research, to improve the durability and reflective performance of RRM before applying it as a building coating, we have developed a new type of RRM by adding a glass covering with high transmission and high strength, and investigated its durability and retro-reflective performance by evaluating changes in solar reflectance and retro-reflectance for a period of 485 days. There was almost no degradation on the surface of RRM, and both its solar reflectance and retro-reflectance showed no significant decrease for the period. Its solar reflectance remained around 0.81, and retro-reflectance around 0.44. Additionally, we simulated the influence of building surfaces with different reflective characteristics on the albedo of urban canyons. A building surface with RRM is the most effective, compared to other materials with diffuse or mirror reflective characteristics. Finally, the influence of RRM coating on building thermal loads was simulated. The cooling loads and the total annual thermal loads were both reduced. Thus, it is possible to apply it as a building coating to both mitigate the heat island and reduce the building thermal loads.

Heat/mass transfer over the plane tip equipped with a full coverage winglet in a turbine cascade: Part 2 – Tip surface data

The effects of h/s (tip gap height-to-span ratio) on heat/mass transfer on the plane (flat) tip surface of a full coverage (FC) winglet have been investigated by employing the naphthalene sublimation technique along with oil film flow visualizations. For a winglet width-to-pitch ratio of w/p=10.55%, the tip gap is widely changed to be h/s=0.68%, 1.02%, 1.36%, 1.70% and 2.04%. The result shows that regardless of h/s, local heat/mass transfer rate on the tip surface is very high on the protruding winglet top surface at the leading edge and on the pressure side. On the other hand, there is relatively low local heat/mass transfer rate on the protruding winglet top surface on the suction side as well as in an area behind the leading edge separation bubble. The tip surface inside the baseline blade profile with the FC winglet is exposed to much less severe thermal load than the baseline plane tip surface with no winglet, whereas total thermal load on the protruding FC winglet is more severe than thermal load on the baseline plane tip surface with no winglet.

Design of the New SC Bus-Line System for the EAST

A new external superconducting (SC) bus-line system consisting of 13 pairs of bus-lines has been designed for the upgrade project of the experimental advanced SC tokamak. The old system integrated into two vacuum ducts will be extended approx. 23 m with new cable in conduit conductors (CICCs) connecting by twin-box lap joints. The leakage currents of the CICCs electrically insulated with four layers of polyimide films and pre-impregnation fiberglass tapes are <10 μA under a 10 kV electrical potential at 77 K, 0.1–100 Pa in helium atmosphere. Each bus-line pair is bound together by 50 % overwrapped with three layers of Kevlar polyester tapes to eliminate its adverse effects of electromagnetic forces with a maximum of 2.44 kN/m. The bus-lines designed with at least four bends are flexible to absorb the thermal shrinkage which is approx. 90 mm in total. The maximum shift of the CICCs is 26.1 mm when cooled down. The total thermal loads to 5 K components in bus-line group 1 and 2 are <0.3 W/m as required.

Cryogenic dual‐temperature low noise amplifier in K band

Future ground stations will require a high level of operational flexibility and, for this reason, the possibility to adjust their receiving performance (i.e. signal-over-noise) is beneficial. This study presents an approach to achieve this flexibility based on a dual-temperature low-noise amplifier, which can be normally operated at room temperature (300 K), reducing the operational and maintenance costs, and at cryogenic temperature (103 K) only when required, for example, for critical mission supports. To demonstrate the effectiveness of this solution, a dual-temperature K-band low-noise amplifier is designed, manufactured and measured for the first time. Critical aspects, such as the stability of the electromagnetic response over the entire temperature range, and the reduction of the thermal load from the entire assembly, fundamental for a fast transition between room and cryogenic temperatures, are discussed. In particular, the low-noise amplifier exhibits a minimum gain of 20 dB over the entire working bandwidth (18–22 GHz) and a maximum noise figure of 2.2 at 300 K and 1.4 at 103 K, with a transition time between room and cryogenic temperature of <120 min because of a total thermal load lower than 1 W.

Commissioning of the DESIREE storage rings – a new facility for cold ion-ion collisions

We report on the ongoing commissioning of the Double ElectroStatic Ion Ring ExpEriment, DESIREE, at Stockholm University. Beams of atomic carbon anions (C−) and smaller carbon anion molecules (C−2, C−3, C−4 etc.) have been produced in a sputter ion source, accelerated to 10 keV or 20 keV, and stored successfully in the two electrostatic rings. The rings are enclosed in a common vacuum chamber cooled to below 13 Kelvin. The DESIREE facility allows for studies of internally relaxed single isolated atomic, molecular and cluster ions and for collision experiments between cat- and anions down to very low center-of-mass collision energies (meV scale). The total thermal load of the vacuum chamber at this temperature is measured to be 32 W. The decay rates of stored ion beams have two components: a non-exponential component caused by the space charge of the beam itself which dominates at early times and an exponential term from the neutralization of the beam in collisions with residual gas at later times. The residual gas limited storage lifetime of carbon anions in the symmetric ring is over seven minutes while the 1/e lifetime in the asymmetric ring is measured to be about 30 seconds. Although we aim to improve the storage in the second ring, the number of stored ions are now sufficient for many merged beams experiments with positive and negative ions requiring milliseconds to seconds ion storage.

Differential effects of temperature variability on the transmission of a marine parasite

Temperature variability is particularly pronounced in intertidal systems. The importance of considering this variability has been increasingly recognised, especially in the context of climate change and disease dynamics. Here, we investigated the effects of temperature variability on the transmission of the intertidal trematode Maritrema novaezealandensis. The experimental treatments were 15 °C (control), 15 + 5 °C daily, 15 + 10 °C every second day, 15 + 15 °C every third day (overall equal thermal loading), and a heat wave treatment (15 + 10 °C daily). Daily 6 h incubations were carried out corresponding to daytime low tides over a 12-day period. Effects on output of transmission stages (cercariae) from infected Zeacumantus subcarinatus snail hosts and transmission success of cercariae to Paracalliope novizealandiae amphipod hosts were quantified, as well as the survival of amphipods. Results showed differential effects on output and transmission success. The number of cercariae emerging was similar for treatments with equal thermal loading, but was substantially increased in the heat wave treatment. Transmission success was highest and comparable for the treatments with regular daily temperature increases (i.e. 15 + 5 °C and heat wave), compared to other treatments. Amphipod survival was not affected by temperature treatment directly, but by the number of parasites infecting an amphipod, as well as amphipod sex. These results demonstrate that cercarial output depends mostly on total thermal loading, whereas successful infection of amphipods is determined by total time above 15 °C. Repeated exposure to ~25 °C, as expected under a heat wave scenario, therefore increases both transmission pressure and success, and hence, the risk of parasite-induced mortality in amphipods.

RAPID THERMAL LOAD ESTIMATION USING A SET OF SMART GRAPHS

The purpose of this research was to develop simple thermal load smart graphs for rapid thermal load estimation. These graphs were generated in order to facilitate a quick estimation of the thermal load. This is especially important when computer-aided heating, ventilation and air-conditioning (HVAC) design software is unavailable. Hundreds of calculations have been carried out using various heat transfer equations and an hourly analysis program (HAP) generated graphs displaying the external and internal sensible and latent heat gains of analyzed spaces. These smart graphs are very user friendly; non-technical individuals can easily calculate the thermal load using these graphs. The smart graphs are time-saving and give results more accurate than thumb rules. In fact, they give a total thermal load estimate that is less than few percent different from the estimate generated using commercial software programs.

Multi-objective energy management of CHP (combined heat and power)-based micro-grid

In this paper, an IEMS (intelligent energy management system) is proposed for optimal operation of a CHP-based micro-grid over a 24-hour time interval. The IEMS aims to find the optimal set points of DERs (distributed energy resources) and thermal and electrical storage systems, in such a way that the total operation cost and the net emission are minimized, simultaneously. For optimal operation of the micro-grid, a smart ESS (energy storage system) is introduced which consists of electrical and thermal storage systems. A comprehensive mathematical model for the ESS and also the economic and environmental objective functions are formulated. To solve the problem, we propose an efficient MBFO (modified Bacterial Foraging Optimization) algorithm. An interactive fuzzy satisfying method is also used to simulate the trade-off between conflicting objectives (cost and emission). To validate the performance of the proposed algorithm, we compare the MBFO algorithm with some other previously proposed analytical methods. Finally, the proposed IEMS is applied to a micro-grid which consists of various DERs, CHP (combined heat and power) system, ESS and thermal and electrical loads. The results show that the proposed IEMS can smartly cover the total electrical and thermal load demands with respect to economic and environmental criteria.

European Experimental Reentry Testbed Winglet: From In-Flight Characterization to SCIROCCO Test

Thiswork is dedicated to the aerothermodynamic characterization, both inflight and atwind-tunnel conditions, of the ultrahigh temperature ceramic winglet that will embark on the European Experimental Reentry Testbed of the European Space Agency. The experimental test has been executed in the Centro Italiano Ricerche Aerospaziali SCIROCCO plasma wind tunnel on a winglet qualification model. The aim of the test was to reproduce the total thermal load,which thewingletwill be subjected to during the reentry trajectory, allowing preflight qualification and verification of materials and sensing equipment. Detailed three-dimensional computations in plasma-wind-tunnel conditions have allowed the verification of the test requirements and provided information about the physical phenomena that can cause dangerous local overpressures and overheatings on the capsule thermal protection system.The actual test condition has been rebuilt after the test bymeans of three-dimensional simulations; particular attention has been paid in modeling surface catalysis and emissivity. Finally, the aerothermodynamic code has been coupled with a thermal code to account for material thermal conduction. Numerical results have been compared in terms of pressure and temperature with experimental measurements showing good agreement.

Minimization of Thermal Impact by Application of Electrode Cooling in a Co‐linear PEF Treatment Chamber

A co-linear pulsed electric field (PEF) treatment chamber was analyzed and optimized considering electrical process conditions, temperature, and retention of heat-sensitive compounds during a continuous PEF treatment of peach juice. The applicability of a jacket heat-exchanger device surrounding the ground electrode was studied in order to provide active cooling and to avoid temperature peaks within the treatment chamber thus reducing the total thermal load to which the product is exposed. Simulation of the PEF process was performed using a finite element method prior to experimental verification. Inactivation of polyphenoloxydase (PPO) and peroxidase (POD) as well as the degradation of ascorbic acid (AA) in peach juice was quantified and used as indirect indicators for the temperature distribution. Peaks of product temperature within the treatment chamber were reduced, that is, from 98 to 75 °C and retention of the indicators PPO, POD, and AA increased by more than 10% after application of the active electrode cooling device. Practical Application: The co-linear PEF treatment chamber is widely used for continuous PEF treatment of liquid products and also suitable for industrial scale application; however, Joule heating in combination with nonuniform electric field distribution may lead to unwanted thermal effects. The proposed design showed potential to reduce the thermal load, to which the food is exposed, allowing the retention of heat-sensitive components. The design is applicable at laboratory or industrial scale to perform PEF trials avoiding temperature peaks, which is also the basis for obtaining inactivation kinetic models with minimized thermal impact on the kinetic variables.

Evaluation of refrigerator/freezer gaskets thermal loads

The gasket total thermal load is calculated as the heat transfer load plus the infiltration load. A method is developed to evaluate the gasket heat transfer load due to convective, radiative, and conductive mechanisms. It uses a quasi-one-dimensional theoretical model combined with experimental and numerical results. The gasket infiltration load is evaluated using the tracer gas method and humidity measurements. The gasket total thermal load obtained by these methods agrees with the load estimated by the reverse heat leak method, with the advantages of having a smaller uncertainty and providing information about the heat transfer along the perimeter of the gasket.

Thermal Management of Wide-Beam Area X-Ray Sources

A wide-beam area X-ray source has been envisioned as capable of delivering X-ray radiation similar to a synchrotron source in terms of the magnitude of photon flux, energy range, and collimation for clinical Diffraction Enhanced Imaging (DEI) applications. Since most of the electron beam energy used to generate the X-rays is deposited in the target material as heat, a cooling system which ensures adequate thermal management is critical to the design. Previous work has shown the feasibility of a prototype scale target with heat fluxes equivalent to those envisioned for an industrial scale system. In this study, a cooling system for an industrial scale target is proposed which is capable of handling a maximum uniform heat flux of 11.693 × 10 6 W/ m 2 for a total thermal loading of 180 kW (3 Amp beam current at 60 kV accelerating voltage). The target behavior was simulated using the CFD code, ANSYS CFX. The simulation results show that target integrity can be maintained for highly non uniform heat fluxes with moderate coolant velocities and pumping powers.

Assessment of thermal performance of different types of masonry bricks used in Saudi Arabia

This paper presents the assessment of thermal performance of nine types of clay brick and two types of concrete brick in use in Saudi Arabia. The results are based on the experimentally measured values of equivalent thermal conductivity. The analysis of the measured data showed that the addition of insulation material either within the masonry brick mix to make the brick more lightweight or through filling insulation material into the holes of masonry bricks increases the thermal resistance significantly. Red clay brick were found more thermally effective than concrete brick. Use of insulating mortar in building walls increases the thermal resistance compared to that of the walls prepared with ordinary concrete mortar. An economic analysis shows that the insulated clay brick (type 7) is the most effective among the types of brick studied as it has the lowest net present value (NPV) of 36.9 $/m 2. The load due to thermal transmission through a building envelope (walls and roof) constitutes an appreciable percent a building’s total thermal load. Therefore, long-term studies of the thermal performance of building materials should be conducted to establish thermally optimal brick for usage in building construction in the Kingdom of Saudi Arabia.

Flux of Positive Ions and Film Growth in Reactive Sputtering of Al-Doped ZnO Thin Films

The reactive magnetron sputtering deposition of Al-doped zinc oxide thin films using a dual magnetron has been studied for a flux of positive ions and the total thermal load onto the substrate. The spatial distribution of both quantities has been studied using a thermal probe and a retarding field analyzer mounted onto a moveable carrier system. The positive ions were found to mostly originate from the plasma sheath at the substrate, with the spatial distribution determined by the plasma density distribution in the coating chamber. The total energy flux to the substrate mainly originated from the plasma, with positive ions only contributing a small part of the total plasma irradiation. In the tested conditions and with the coater examined, the quality of the deposited films mainly depends on oxygen distribution on the substrate and is not a direct consequence of the total energy flux to the substrate.