Heat Load Measurements Research Articles

Calorimetry probe for runaway electron heat load measurement at COMPASS.

Runaway electrons, accelerated in a tokamak discharge to high energies (tens of MeV), can cause serious damage to plasma facing components. Therefore, it is important to develop effective mitigation strategies to reduce the risk of tokamak damage. To study the effects of various mitigation strategies, a dedicated diagnostic, the calorimetry probe, was developed at the COMPASS tokamak. This probe successfully measured the heat loads caused by runaway electrons directly, using a set of temperature sensors embedded in a graphite body. Deposited energy measured by the probe ranged from a few hundred joules up to (15 ± 1)kJ, while the mean deposited energy was (4.5 ± 1.1)kJ. The design of the probe and the initial results from 250 discharges covering four experimental campaigns dedicated to runaway electron studies (2019-2021) are presented in this article.

Thermal performance analysis and cryogenic experimental measurements of the 166.6 MHz cavity cryomodule for the High Energy Photon Source

The 166.6 MHz radio frequency (RF) system with five superconducting HOM damped cavities is adopted to accelerate the 200 mA electron beam in the storage ring of the High Energy Photon Source (HEPS). The 166.6 MHz cavity cryomodules have been designed, constructed and horizontal tested at IHEP since the beginning of 2019. The thermal performances of the cryomodule are analyzed by numerical simulations which take into account the main contributors to the static heat loads at various temperature levels. The experiment investigations including the cool down, operating with RF power and static heat load measurements of the cryomodule are performed in the liquid helium cryogenic system. The calculated static heat loads have been compared with the experimental measurements, and the results show that deviations between the calculated heat loads and available experimental measurements at 4.2 K temperature level are within a small range, which indicates that thermal simulations are accurate. The detailed operating parameters in the cryogenic environment are reported.

Predict-IT - Forecasting District Heating Loads

In the realm of many thermal energy systems, and particularly within district heating networks, heat load forecasts play a pivotal role in optimizing system operation and efficient infrastructure usage. While district heating operators routinely log measurement data, its potential remains underutilized. One essential application of such data is forecasting a network’s heat load based on historical data records. Such forecasts can improve the efficient usage of plant infrastructure and facilitate predictive operational strategies. This paper introduces ”Predict-IT”, a web-based platform designed to standardize the entire forecasting pipeline, making the generation of predictions largely independent of expert knowledge. The Predict-IT platform is powered by a state-of-the-art long short-term memory (LSTM) based neural network algorithm which only requires very little inputs (measured heat load and ambient temperature) to deliver satisfying forecasting accuracy, even a couple of days ahead. The prediction algorithm is validated on two data sets from local Austrian district heating networks, showing the general applicability of the LSTM-based neural network, given an appropriate set of hyperparameters. The Predict-IT platform simplifies the process of forecasting heat loads into a few discrete steps: data upload, algorithm training, heat load forecast generation, and visualization of forecasts. The source code will be open-source, and deployment and installation will be facilitated by an easily installable Docker solution.

Heat load model for small-scale CHP planning

Present-day world energy policy is based on two main directions: energy efficiency and environmental protection. Efficient Combined Heat and Power production is one of the energy consumption effective methods, where CHP production from the renewable fuels is preferable. [1] In order to plan for the most economical, technical and environmental optimal CHP system, it is especially important to estimate the expected heat demands and heat load profiles for the district heating area. This paper describes a method for estimation of heat load profile for a given district heating area by dividing it to three different heat load types: Temperature depended heat load; Constant heat load; User defined heat load. The paper provides a complete description of above mentioned heat load types, equations as well as calculation examples. Calculation results are compared to hourly measured heat loads to estimate accuracy of a proposed model.

Conceptual design of Fiber Bragg Grating temperature sensors for heat load measurements in COMPASS-U plasma-facing components

Information about the temperature of plasma-facing components is important for a reliable tokamak operation. A temperature monitoring system using Fiber Bragg Grating (FBG) sensors is foreseen for the new tokamak COMPASS Upgrade, which is currently starting its construction. This diagnostic can be a valuable complement to IR thermography, thermocouples, and Langmuir probe divertor diagnostics. The system will be optimized to estimate the steady-state and transient heat loads, such as runaway electrons, on the divertor and limiters. In this contribution, current progress in the design of the FBG sensors for the COMPASS-U initial open divertor and guard limiters is presented. The heat flux on the plasma-facing components is modeled for diverted and first phase circular plasma scenarios by the PFCFlux code. The subsequent heating and the mechanical strain in the components dedicated for the placement of the sensors is simulated by the finite element analysis software ANSYS. Using these results, the optimal placement and configuration of the sensors are determined with respect to the anticipated maximum temperature and gradients.

Thermal design and performance of low beta cryomodule for CAFe

China initiative Accelerator Driven System (CiADS) has developed several kinds of cryomodules for superconducting proton linac at IMP. The low beta cryomodules had been designed, fabricated, assembled, and tested for the linac. To meet the requirements of minimizing heat transfer and operational stability, the thermal design and performance of low beta cryomodules have been studied. In this paper, finite element analysis and numerical calculation have been carried out on the design of important components such as thermal insulating support, bellows, thermal shield, power coupler, current leads and so on. Then the heat loads at various temperature levels have been summarized. Besides, the performance of the cryomodules including the cool down, equipment operating data, and heat load measurements are reported. The trial test result of low beta cryomodules shows that the various technical indexes satisfied the technical requirements.

Exchange of Heat Radiation between Human Body and Urban Environment: Characterization in Visible, Near-Infrared, and Far-Infrared Regions

In urban environments, radiation energy from the sun becomes a heat load on the human body. The radiation energy can be divided into visible, near-infrared, and far-infrared wavelengths. Far-infrared radiation is re-emitted from structures that have been warmed by the sun. On the other hand, visible and near-infrared light comes directly or reflected from structures. However, previous studies have measured environmental changes using only far-infrared cameras to study urban heat island (UHI) countermeasures. Therefore, it is important to measure the environmental radiation energy at each wavelength region to properly discuss the cause of the heat load. To conduct the measurements, we used three cameras operating at different wavelengths: visible, near-infrared, and far-infrared. In addition, the measurements were conducted in different urban locations, seasons, and weather conditions in the Tokyo area of Japan, an urban metropolis. The results for far-infrared wavelengths show that, in summer when the temperature is high, all structures except the sky have a positive heat load on the human body, while, in winter or cloudy weather when the temperature is low, the heat load on the human body is negative. The results of heat load measurements at visible and near-infrared wavelengths show that the heat load varies greatly depending on the proportion of sky, plants, and buildings, despite the proportion of ground area being the same. These results indicate that the differences in radiation wavelengths need to be considered when considering reducing the heat load on the human body in urban environments. Therefore, the proposed method could contribute to the development of more effective UHI countermeasures by measuring in a various environments and countries.

Extended state observer-based model predictive temperature control of mechanically pumped two-phase loop: An experimental study

Mechanically pumped two-phase loop (MPTL), as an emerging two-phase heat dissipation transformational technique, has made booming progress in some critical but tough cases such as space stations and high-performance chips. However, accurate temperature regulation of MPTL is intractable due to periodic heat load disturbance, measurement noise, and micro-channel boiling nonlinearity. To address these issues, an extended state observer-based model predictive control (ESOMPC) strategy is developed in this paper. To describe the process model, this paper builds an MPTL platform equipped with a micro-channel evaporator, based on which a series of sinusoidal heat load variation is carried out to show the effects on the wall temperature. Open-loop step experiments are then conducted in terms of flow rate of the working fluid so that the process model can be identified and the nonlinearity can be analyzed. Then, the ESOMPC is developed by incorporating the disturbance information in the optimization framework of the MPC. The ESO part is utilized to estimate the unknown disturbances and compensate the nonlinearity of MPTL, and thus enhance the disturbance mitigation property of the MPC algorithm. Finally, the closed-loop experiments verifies the efficacy of the proposed solution, showing smaller temperature fluctuation and shorter settling time than the conventional controller. The results indicate the great potential of the proposed ESOMPC in enhancing the temperature control accuracy of MPTL in terms of thermal management performance.

Introduction of the liquid nitrogen transfer line for TPS beamline endstation

At Taiwan Photon Source (TPS), the main liquid-nitrogen (LN2) transfer line of length 600 m for beamline endstations was installed in 2015. It formerly supplied LN2 to maximum 24 beamline endstations. Beamline endstation 13A, of which the aim is advanced and general studies of biological structures and structural kinetics in solution or condensed forms under environmental simulations, from atomic to micrometre scale and time resolution from microsecond to minute, was installed during 2018 and 2019. We designed and self-manufactured one LN2 transfer line according to the requirement of beamline endstation 13A, to supply LN2 into the double-crystal monochromator (DCM), to solve the problem of thermal deformation of the crystal. Otherwise the keep-full device was designed to replace the phase separator of the chiller. In this paper we present the pipeline design, performance testing, keep-full device, pressure reducer, noise reduction and heat-load measurement.

Controlling the size of non-axisymmetric magnetic footprints using resonant magnetic perturbations

The structure of the non-axisymmetric heat load distribution at the divertor plates is determined not only by the toroidal but also from the poloidal spectrum of non-axisymmetric field perturbations. Whether they are intrinsic, like error fields, or they are applied through 3D coils, the non-axisymmetric fields produce complex 3D edge magnetic topologies (footprints) that alter the properties of the heat and particle flux distributions on the divertor target plates. In this manuscript, a study of the impact of applied 3D field poloidal spectrum on the footprint size and structure is done for the DIII-D tokamak using the resistive MHD code M3D-C1 coupled with the field line tracing code TRIP3D. To resolve the impact of the poloidal spectrum of the magnetic perturbation, the relative phase of the two rows of in-vessel 3D coils used to produce both a n = 2 and a n = 3 perturbation is varied, where n is the toroidal harmonic of the magnetic perturbation. This shows that the largest footprint is predicted when the relative phase of the two rows is close to zero, which is also where the resonant coupling with the plasma is maximized. These results suggest that it will be challenging to decouple the footprint size from the requisite resonant coupling for RMP–ELM control. The correlation between the measured heat load and particle flux distributions at the outer divertor plates in DIII-D and the magnetic measurements is in good agreement with the predicted dependence of the magnetic footprint size on the amplitude of the resonant component of the plasma response.

Divertor power loads and scrape off layer width in the large aspect ratio full tungsten tokamak WEST

WEST is a full W tokamak with an extensive set of diagnostics for heat load measurements especially in the lower divertor. It is composed by infrared thermography, thermal measurement with thermocouples and fibre Bragg grating embedded few mm below the surface and flush mounted Langmuir probes. A large database including different magnetic equilibrium and input power is investigated to compare the heat load pattern (location, amplitude of the peak and heat flux decay length) on the inner and outer strike point regions: from the first ohmic diverted plasma (obtained during the second experimental campaign C2 in 2018) up to the high power (8 MW total injected) and high energy (up to 90 MJ injected energy in lower single null configuration) experiments performed in the last experimental campaign (C4 in 2019). Concerning the peak location, a good agreement (<1 cm) is obtained between thermal inversions and flush-mounted LP measurements. The peak heat flux from the whole set of diagnostics is in good agreement and mainly in the ±20% range, while the heat flux decay length reported on the target shows significant discrepancy between diagnostics and location in the machine (±40% range). Despite such discrepancy, heat flux decay length at target is found to scale mainly with the magnetic flux expansion through the variation of the X-point height, as expected. The improved plasma performances achieved during C4 enabled to reach significant heat load in the divertor, up to 6 MW m−2 with 4 MW of additional heating power showing the capability to reach the ITER relevant heat load (10 MW m−2 steady state) with about 7 MW of additional power in L-mode discharge. The heat load distribution is clearly asymmetric with a 3/4 and 1/4 distribution on the outer and inner strike point region respectively for the parallel heat flux.

Characterization of Transient Wall Heat Load for a Low NOx Lean Premixed Swirl Stabilized Can Combustor Under Reacting Conditions

Abstract As stringent emissions controls are being placed on gas turbines, modern combustor design optimization is contingent on the accurate characterization of the combustor flame side heat loads. Power generation turbines are increasingly moving toward natural gas, biogas, and syngas, whose composition is highly dependent on the sourcing location. With fuel flexible nozzles, it is important to understand the heat load from various gas mixtures to optimize the cooling design to make sure the liner is not under/over cooled for some mixtures as this has a larger effect on NOx/CO emissions. In addition to knowing the heat load distribution, it is important to understand the peak heat load under start/stop transient conditions which tend to be much higher than steady-state/cruise altitude heat loads. The present work focuses on the experimental measurement of the transient heat load along a can combustor under reacting conditions for a swirl-stabilized premixed methane–air flame. Tests were carried out under various equivalence ratios, Reynolds numbers, and pilot fuel flowrate. An infrared camera was used to measure the inner and outer wall temperatures of the liner to calculate the liner heat load. Particle image velocimetry (PIV) was employed to visualize the flowfield for various reacting conditions studied in this work. Based on the heat transfer study, a detailed report of transient heat load along the length of the liner wall has been presented here. Initial start transient heat load on the liner wall is ∼10–40% more than the steady-state heat load.

Thermal analysis and experimental study of cryostat for superconducting wiggler of the HEPS-TF

As an insertion device, the superconducting wiggler has been developed for about 40 years, the superconducting magnet of which is usually made of NbTi and set in a cryostat. The performance of the cryostat is vital to the success of the superconducting wiggler. In this paper, a cryostat of the superconducting wiggler with 32 poles and 2.6 T field for the High Energy Photon Source Test Facility (HEPS-TF) was developed in the Institute of High Energy Physics (IHEP). In the cryostat, a novel design of thermal structure and cooling capacity distribution was proposed. Compared with the conventional two thermal shields, the single thermal shield was adopted to simplify the mechanical design, which was extended to the outside of the vacuum chamber to decrease the heat loads at 4.2 K. The current leads were optimized to minimize the heat loads at 60 K. After the systematic thermal analysis and optimization, the total heat load was covered by the four Gifford-Mcmahon cryocoolers successfully. In the experiment, the measured heat load was 3.85 W with magnet current of 320 A and beam of 250 mA. And the residual cooling power was 0.65 W.

Cross diagnostics measurements of heat load profiles on the lower tungsten divertor of WEST in L-mode experiments

WEST is a full metallic tokamak with an extensive set of diagnostics for heat load measurements. In this paper, heat loads on the lower divertor of WEST are investigated using two independent methods. A first method relies on the thermal inversion of temperature measurements from arrays of thermal sensors embedded a few millimeters below the surface, while the second consists in the inversion of black body surface temperatures measured by infra-red (IR) thermography. The challenge of IR based temperature measurements in the full metal environment of WEST is addressed through a simplified model, allowing to correct for global reflections and low surface emissivities of tungsten surfaces. A large database (>100 L-mode discharges) is investigated. It is found that the energy absorbed by an outer divertor tile during a plasma discharge is closely estimated by the two diagnostics, over a large set of experimental conditions. A similar match is also found for the peak heat flux value on the outer target. The toroidal modulation of target heat loads by magnetic ripple is found to be consistent with the geometrical projection of a parallel heat flux component. Additionally, the heat flux channel width at the target is found to scale linearly with the magnetic flux expansion as expected. These observations give confidence in the robustness of the data from both diagnostics, and confirm the simple geometrical rules at use in the description of heat flux deposition on divertor targets. However, it is shown that the heat flux channel width estimated from infra-red thermography is about three times lower than the width estimated from embedded measurements, which is still under investigation.

A two-condenser pulsating heat pipe for use as a passive thermal disconnect in redundant cryocooler implementations

A proof-of-concept, two-condenser nitrogen pulsating heat pipe (PHP) for use as a passive thermal switch in applications with redundant cryocooler installations is developed and tested. The PHP design comprises two independent PHP condensers, each thermally linked to an independent cryocooler cold head, with the two associated PHP evaporators attached to a common cold plate heat load. The design allows the cold plate heat load to be continuously cooled when one cryocooler is non-operating. This is accomplished by leveraging the thermal isolation provided by dryout in the PHP associated with the non-operating cryocooler to limit the parasitic load on the common cold plate (and therefore on the remaining operating cryocooler) from the ambient environment. Mechanical actuation is not required as the PHP thermal switch is fully passive. Instrumentation is included in the proof-of-concept device to measure the heat loads and effective thermal conductivities of each PHP. The design of the system is presented in detail, along with preliminary measurements of PHP heat loads and PHP effective thermal conductivities in states of both pulsating advection and dryout.

Characterization of heat load profiles in buildings and their impact on demand side flexibility

A data set of heat load measurements for 197 buildings from different building categories (apartment blocks, hotels, nursing homes, offices and schools), have been analysed to evaluate the potential for peak shaving. A moving average filter is applied to investigate how smoothening of the load profiles can reduce the peak loads. It is shown that for short term peak shaving, apartment blocks and hotels have the highest potential (around 8% for a two hour period), while for longer term peak shaving, the results are more even for all the building categories. Schools stand out, with a large difference in heat consumption between inside and outside opening hours, leading to a large flexibility potential on daily basis, but this would require a large amount of stored energy. As it is difficult to control, and thereby reduce the peaks for unknown loads, a prediction model is applied to the data, to analyse the predictability. It is shown that the peak shaving potential is reduced 90-30 % when analysing only the predictable loads. The biggest difference is in the short-term potential for apartment blocks and hotels, while difference is smaller in the long-term (24-hour) peak shaving potential.

Heat flux evaluation in a multi-element CH4/O2 rocket combustor using an inverse heat transfer method

Heat load measurements in experimental lab-scale rocket combustors are essential in order to obtain information about the mixing and energy release of the propellants, the injector/injector interaction as well as the injector/wall interaction. The present work demonstrates an efficient inverse method for estimating the spatially resolved heat flux distribution at the hot gas wall of multi-element, actively cooled engines using the information provided by temperature measurements in the material. This inverse method implements Nusselt-correlations for the estimation of the wall heat transfer coefficient in the cooling channels and a Jacobi-matrix based optimization algorithm for the calculation of the hot gas side heat flux. The method is applied for the evaluation of CH4/O2 test data. A water-cooled 7-injector rocket combustor is investigated, which is operated at the Chair of Turbomachinery and Flight Propulsion (LTF) of the Technical University of Munich (TUM). The use of the inverse method gives significant information about the axial and azimuthal distribution of the heat flux. The azimuthal distribution sheds light into the interaction between the individual flames. Specifically, the angular position of maximal heat flux appears to shift from directly above the injector elements towards the positions between two neighboring elements, implying the presence of a strong vortex system pushing hot gas directly onto the wall. The obtained results agree qualitatively with RANS simulations of the hot gas flow.

Thermal performance analysis and operation of the spoke cavity cryomodules for C-ADS Injector-I

The Chinese Accelerator Driven Sub-critical system (C-ADS) is an important strategic research that is based on a high energy proton beam for nuclear waste transmutation. To meet the requirements of stability and reliability of the lower energy part, two identical Injectors are operated in parallel. The Injector-I is designed and constructed by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS) in Beijing, China. The Injector-I linac with two accelerating cryomodules (named CM1 and CM2) successfully accelerated the proton beam to 10.67 MeV with the beam current of 10.11 mA in pulse mode and 10.0 MeV with a beam current of 1.6 mA in CW (continuous wave) mode.The cryomodules have been designed, fabricated, assembled and commissioned at IHEP since the beginning of 2012. The thermal performances of the cryomodules were analyzed with numerical simulations and the empirical calculations take into account all the main contributors (support posts, multilayer insulation, current leads, power couplers and cavities) to the static and dynamic heat loads at various temperature levels. Two designs of current leads are developed and analyzed, and the case 2 current leads are tested and used in the CM2. The estimated static heat loads by analysis have been compared with the available experimental measurements. The operation experiences including the cool down, operating parameters and heat load measurements are reported, and the results were shown that the cryomodules can keep in a stable operation at 2 K and 30 mbar ±10 Pa.

Design and thermal performance of spoke cavity prototype cryomodule of the Chinese Accelerator Driven Sub-critical system Injector-I

The Chinese Accelerator Driven Sub-critical system (C-ADS) Injector-I is designed and constructed by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS) in Beijing, China. The test cryomodule (TCM), housing two 325 MHz spoke cavities and two solenoids and operating at 2 K, has been designed, assembled and commissioned since the beginning of 2012. The C-ADS Injector-I linac with the TCM successfully accelerated the proton beam to 3.68 MeV with the peak current of 10.1 mA in pulse mode. It is the world’s first prototype of spoke cavity cryomodule with beam, and is an important step in the qualification of the cryomodule before series productions. This paper describes the detail of the design, operation and thermal performances of the prototype cryomodule. The analysis takes into account the heat loads of the main components (support posts, multilayer insulation and cavities) at various cryogenic temperature levels. The estimated heat loads of the cryomodule have been compared with the available experimental measurements, and the cryogenic deformations by simulation is verified by the experimental measurements by the wire position monitors (WPMs). The operation experiences including the cool down, alignment and heat load measurement are reported. • The 325 MHz spoke cavity prototype cryomodule has been designed, assembled and commissioned. • The thermal performance of the bottom-supported cryomodule has been proved firstly worldwide. • The cryomodule can be in a stable operation at 2 K and 31 mbar with beam. • The operation experiences including the cool down, alignment and measurement of heat loads are reported. • The linac with cryomodule had been accelerated successfully to 3.68 MeV@10.1 mA in pulse mode.

Thermal performance of the new superfluid helium vertical test cryostats for magnet tests at CERN

In the frame of the R&D program of the HL-LHC, the upgrade of the Large Hadron Collider (LHC), CERN augmented its test facility with two new large-scale vertical test stations for superconducting magnet testing. The cryostats composing the core of these test stations share design features but are of different dimensions: one allows testing magnets up to 1.5 m diameter, 2.5 m long for a maximum weight of 15 t, while the other can accommodate magnets up to 0.9 m diameter, and 5.5 m long for a maximum weight of 18 t. These test stations are designed to operate at 1.3 bar and at controlled temperatures in the range 1.9 - 4.5 K. They can provide for safe dissipation of stored energy in the magnet coils of up to 10 MJ. After a brief description of the cryostats, this paper describes the qualification measurements of heat loads at 4.5 K and 1.9 K of both cryostats, some design enhancements that were made and the performance improvements obtained.