Typical Heat Load Research Articles

Experimental Investigation of a Helium-Cooled Breeding Blanket First Wall under LOFA Conditions and Pre-Test and Post-Test Numerical Analysis

The experimental investigation of a prototypical set-up simulating a loss of flow accident in a helium-cooled breeding blanket first wall mock-up under typical heat load conditions is presented. The experimental campaign reproduces the expected DEMO thermal-hydraulics conditions during normal and off-normal situations and aims at providing some insight into the fast transients associated with the loss of flow in the blanket first wall. The experimental set-up and the definition of the experimental matrix are discussed, including pre-test analysis performed in support of these activities. The major experimental results are discussed, and a procedure of using the acquired data for validating and calibrating the RELAP-3D model of the mock-up is introduced. All these activities contributed to the creation of a relevant theoretical and practical experience that can be used in further studies concerning incidental transients in real-plant scenarios in the framework of DEMO plant fusion safety activities.

Heat transfer in cryosurgical device with an extended applicator

This paper is aimed to study the prototype of cryosurgical device with an extended applicator. Three experiments were conducted. First, an experiment without heat load showed temperature distribution on extended applicator and its cooldown time. Second, an experiment with a typical heat load (when the applicator contacts the biotissue phantom) showed the impact of heat load on the surface temperature and on its cooldown time in this case, as well as the temperature at the control points inside the biotissue phantom and the dynamics of growth, shape and size of the freezing region. The third experiment was equivalent to the second, but without temperature sensors on the applicator surface for better freezing region visualization. Also, after the liquid nitrogen supply is stopped, the dynamics of thawing are considered. Data on the actual temperature during cryoexposure should help give basic recommendations for developing a cryoexposure technique with increased dosing accuracy.

Modelling of room air temperature profile with displacement ventilation

An accurate temperature gradient calculation is essential for displacement ventilation (DV) system design, since it directly relates to the calculation of supply air flow rate. Several simplified nodal models were developed and implemented in the various building simulation programmes to estimate the temperature stratification in rooms with displacement ventilation. However, the most commonly used models do not take into account the types and locations of the heat loads in rooms with DV. As a result, the calculated air temperature in the occupied zone can defer from the real one by 2–3 °C, which causes poor thermal comfort and inadequate sizing of the ventilation and cooling systems. In the present study, the nodal model was proposed to provide a simplified technique to predict the vertical temperature gradient in rooms with DV. In addition, the effect of the room height and locations of the indoor heat sources were studied for the typical office environment. The measurement data were compared with the existing nodal models and the proposed nodal model in terms of predicting the occupied zone temperatures. The presented nodal model demonstrates an accurate calculation of the temperature gradient for the typical heat loads and combinations of them.

A variation focused cluster analysis strategy to identify typical daily heating load profiles of higher education buildings

This paper presents a variation focused cluster analysis strategy to identify typical daily heating energy usage profiles of higher education buildings. Different from the existing cluster analysis studies which were primarily developed using Euclidean distance as the dissimilarity measure and tended to group the daily load profiles with similar magnitudes, Partitioning Around Medoids (PAM) clustering algorithm with Pearson Correlation Coefficient-based dissimilarity measure was used in this study to group the daily load profiles on the basis of the variation similarity. A comparison of the proposed strategy with a k-means cluster analysis with Euclidean distance as the dissimilarity measure was also performed. The performance of the proposed strategy was tested and evaluated using the three-year hourly heating energy usage data collected from 19 higher education buildings in Norway. The results demonstrated the effectiveness of the proposed strategy in identifying the typical daily energy usage profiles. The identified typical heating load profiles provided the information such as the peaks and troughs of the daily heating demand, daily high heating demand period and daily load variation. The identified profiles also helped to categorize multiple buildings into different groups in terms of the similar energy usage behaviors to support further energy efficiency initiatives.

Heat load patterns in district heating substations

Future smart energy grids will require more information exchange between interfaces in the energy system. One interface where dearth of information exists is in district heating substations, being the interfaces between the distribution network and the customer building heating systems. Previously, manual meter readings were collected once or a few times a year. Today, automatic meter readings are available resulting in low cost hourly meter reading data. In a district heating system, errors and deviations in customer substations propagates through the network to the heat supply plants. In order to reduce future customer and heat supplier costs, a demand appears for smart functions identifying errors and deviations in the substations. Hereby, also a research demand appears for defining normal and abnormal heat load patterns in customer substations. The main purpose with this article is to perform an introductory analysis of several high resolution measurements in order to provide valuable information about substations for creating future applications in smart heat grids. One year of hourly heat meter readings from 141 substations in two district heating networks were analysed. The connected customer buildings were classified into five different customer categories and four typical heat load patterns were identified. Two descriptive parameters, annual relative daily variation and annual relative seasonal variation, were defined from each 1year sequence for identifying normal and abnormal heat load patterns. The three major conclusions are associated both with the method used and the objects analysed. First, normal heat load patterns vary with applied control strategy, season, and customer category. Second, it is possible to identify obvious outliers compared to normal heat loads with the two descriptive parameters used in this initial analysis. Third, the developed method can probably be enhanced by redefining the customer categories by their indoor activities.

Neutron computed tomography of plasma facing components for fusion experiments

Abstract In nuclear fusion experiments, divertor plates are used to remove energy and particles from the plasma. These divertor plates can be made of water-cooled copper heat sinks covered by carbon fiber composite (CFC) protection tiles. During operation, surface temperatures in excess of 1000 °C are reached for typical heat loads of 10 MW/m 2 . The large mismatch in the coefficients of thermal expansion for CFC and Cu causes high stresses and possibly bonding defects. Growing joint defects, which lead to unacceptable overheating of the protection tiles, are critical for the lifetime of the components. A prototype component was subjected to 10,000 cycles at 10 MW/m 2 to study the crack growth mechanism. Neutron computed tomography offers the possibility to analyze such structures on centimeter-sized samples non-destructively with a high spatial resolution. At the ANTARES neutron imaging facility of the FRM II reactor, the samples were loaded with a contrast agent and examined with neutron computed tomography.

Estimation of carbon fibre composites as ITER divertor armour

Exposure of the carbon fibre composites (CFC) NB31 and NS31 by multiple plasma pulses has been performed at the plasma guns MK-200UG and QSPA. Numerical simulation for the same CFCs under ITER type I ELM typical heat load has been carried out using the code PEGASUS-3D. Comparative analysis of the numerical and experimental results allowed understanding the erosion mechanism of CFC based on the simulation results. A modification of CFC structure has been proposed in order to decrease the armour erosion rate.

Development of plasma facing components at JAERI

The development and design of the divertor plate in JAERI are presented. Small divertor models are fabricated and tested in an electron beam heating facility in the JAERI. Typical heat load is 10 MW/m 2. The divertor models consist of CFC or isotropic graphite/Cu bonded structures. A twisted tape is inserted to enhance heat transfer. It is shown after 1000 thermal cycle tests that CFC-Cu bonded structures can endure against a stationary heat load of 10 MW/m 2. A prediction technique, which consists of three analytical steps, is developed to estimate deformation of the divertor plate and stress in the cooling tube. A maximum stress of 350 MPa is obtained for the CFC-Cu divertor plate. Displacement of the divertor plate reduces to ±2 mm with supporting structures.

Study on divertor materials and heat load experiments with electron beam facility

Typical heat load conditions on a divertor plate in a fusion reactor are 2 MW/m 2 at normal operation and 500 MW/m 2 × 5 ms at plasma disruption. Test Materials I and II were prepared for basic material tests, corresponding to the followings, (1) Design I: tube structure of copper alloy with or without protection layer, and (2) Design II: graphite tiles brazed to a metal tube. Test Material I is a plate of a OMC Cu-Cr-Zr alloy. The molybdenum coating (∼500 μm) was applied by plasma spray. Test Material II is graphite brazed to a molybdenum base plate. Heat load experiments were performed on the test materials for normal operation or disruption simulation by using a 120 kW electron beam facility. Thermomechanical and erosion analyses were also performed. This basic study showed that these two types of materials have good characteristics at the typical heat load conditions.

Thermal-structural analysis of large space structures - An assessment of recent advances

Recent advances in modeling, analyzing, and understanding the thermal-structural responses of large space structures are reviewed, and uncertainties in the thermal-structural analysis are identified. Typical heat-load, thermal, and structural analyses requirements for large space structures are discussed using a design for a future large spacecraft as an example. The current status of heating, thermal, and structural analyses is then reviewed, and computer programs used in research and design are discussed. The need to develop efficient methods for integrating the interdisciplinary analyses is emphasized.

Small Cryopump with Integral Refrigerator

Performance characteristics of a compact, self-contained cryopump are described. Inputs required are electrical power and liquid nitrogen. A chevron-shielded 1000-cm2 cryopanel cooled to below 30 °K by a modified Taconis-cycle refrigerator had a pumping speed of 3200 liter/sec for air at pressures below 5×10−4 Torr. The speed for argon was 2200 liter/sec. Calculations of typical heat loads show that a 1-W refrigerator should be capable of supporting nitrogen-pumping speeds as high as 10000 liter/sec. Pumpdowns on an unbaked, 150-liter-volume stainless steel chamber yielded short-term ultimates of 4×10−9 Torr with use of a 50-liter/sec auxiliary sputter-ion pump for noncondensables. By subliming titanium onto liquid-nitrogen-chilled surfaces, ultimates of ∼2×10−10 Torr were observed.