Heating Power Research Articles

Prediction of polarization curves of PEMFC membrane electrode assembly using artificial intelligence technics

Proton exchange membrane fuel cells (PEMFCs) are used commercially in automobiles, buses, uninterruptible power supplies, and combined heat power systems, holding a significant place in the fuel cell market. Fuel cell performance is characterized by polarization curves in design and manufacturing processes. This study predicts a PEMFC’s polarization curves using comparative artificial intelligence (AI) models trained and tested under different operational conditions. The AI model inputs are cell temperature, humidity, anode-cathode flow, and membrane resistance. The outputs are cell voltage and current density. The model outputs are compared with experimental values for 50°C, 100% humidity using MATLAB software. The average Root Mean Square Error (RMSE) for the ANFIS prediction is 0.056112, while for the ANN prediction it is 0.011919. These results indicate that the Artificial Neural Network (ANN) method outperforms the Adaptive Neuro Fuzzy Inference System (ANFIS) in predicting the behavior of the PEMFC’s Membrane Electrode Assembly (MEA). The models showed promising results with high accuracy.

OPTIMIZATION OF PECTIN EXTRACTION FROM SUGAR BEET PULP USING MICROWAVE TREATMENT

Pectin is a natural heteropolysaccharide contained in plant cell walls and plant waste. In recent years, various alternative methods (enzymatic, microwave, ultrasonic) have been used to increase the yield of pectin, which can increase the efficiency of the process, pectin yield and improve quality. The principal advantages of using microwaves for the extraction of pectin from plant waste materials are the significant reduction in processing time, the higher yield of the natural polymer and the quality maintenance due to the more gentle processing conditions. The purpose of the work is to improve the method of pectin extraction from beet pulp using microwave treatment. Experiments were carried out to establish the optimal conditions of polysaccharide extraction. The pectin extraction was optimized by varying the microwave power, the pH of the medium, the processing time, the type of extracting agent (citric, malic, hydrochloric and acetic acids) and the ratio of beet pulp to extracting agent. A titrimetric method was used to determine the degree of esterification and the uronide component. Results and discussion. Extraction of pectin from sugar beet pulp includes the following main steps: polymer extraction by microwave treatment, pectin purification and drying. Among the studied parameters, the ratio of beet pulp to extracting agent and microwave processing time had a significant effect on the yield and properties of pectin. The highest yield of pectin (5.7%) was achieved at a heating power of 520 W, pH - 2.0, processing time of 30 minutes, using citric acid as the extraction agent and a beet pulp to extraction agent mass ratio of 15:1. IR spectra of the extracted pectin show the presence of characteristic bands typical of the pectin spectrum. Conclusions. Varying the parameters of pectin extraction from sugar beet pulp using microwave treatment allowed to increase the yield of pectin with desired characteristics. The perspective of using ecologically pure organic acids (citric and malic acids) as an extracting agent is shown.

Experimental study on the thermal runaway hazard quantification and its assessment parameters in the lithium-ion battery

Thermal runaway (TR) is a thermal disaster in the lithium-ion battery (LIB). The TR hazard in the LIBs with different battery characteristic and under different TR triggering method is distinctive, and it is of great significance to quantify the TR hazard as a criterion for TR quantified suppression for its further development. This study has investigated the TR hazard assessment parameters (HAPs) in the batteries of different rated capacity Rc and battery number N under different TR triggering method, and raised a novel method for TR hazard quantification based on these HAPs. The results show: (1) under different triggering method, the HAPs are increased with the increase of overcharging rate Cr and the decrease of heating power Ph, but not explicit with the change of punching speed Ps, and increased with Rc in most cases; (2) the quantified TR hazard HTR-q is greater in the cases of overcharging and punching, and is 1.52 times greater in the confined space under the same case in the open space. Besides, The Rc and HTR-q form a quadratic function relationship, and N and HTR-q a linear relationship. Moreover, a computing model of HTR-q is proposed with the input of, self-characteristics of battery Sc and TR triggering intensity It, which exhibits the average error of 6 % approximately. This is expected to become a novel method in TR hazard assessment, and offer guidance on the setting of key parameters for TR suppression.

Design and experimental analysis of a novel thermal diode with asymmetric heat transfer inspired by feather

To overcome the limitation of isotropic heat transfer of traditional heat pipes, a novel thermal diode with asymmetric flow resistance vapor channel inspired by the goose feather fibers is proposed in this study. The thermal performance of novel thermal diode is experimentally investigated. Results show that under the wide range of operating conditions, the thermal resistance of one end surpasses the thermal resistance of the other end, indicating its excellent thermal rectification capability. Under the filling ratio of 10 % and heating power of 7.5 W, the maximum thermal resistance of the thermal diode is 5.23 times the minimum thermal resistance, demonstrating excellent asymmetric heat transfer performance. Experimental results demonstrate that the novel thermal diode proposed in this study can easily change its unidirectional heat transfer direction by simply adjusting the internal filling ratio, showing significant application potential in the fields of thermal control system.

Numerical study on the heat transfer features of concurrent forced nano-PCM emulsion/water flows in a double concentric-tube configuration

To provide a feasible heat dissipation solution for a high heat flux, in this study, the internal flow and heat transfer characteristics of an externally heated concentric double tube were numerically studied via the implicit finite difference method. The outer ring and inner tube were filled with a phase change nanofluid and water, respectively. The parameter ranges were as follows: the mass fractions of the phase change material (PCM) emulsions were 2.04 %, 2.91 %, and 7.11 %, the relative flow ratio was 0.33–4.0, the heat power inputs were 70 W and 150 W, and the total tube flow rates were 304.83 cm3/min and 465.98 cm3/min. The results showed that incorporating PCM emulsions can effectively improve heat transfer performance; however, the PCM concentrations, heating conditions, and outer-annulus/inner-tube flow rates (relative flow ratios) must be properly matched so that the phase change of the working fluid occurs in the expected section. Within these parameter ranges, in the heated section, the latent heat utilization of the PCM emulsion is lower than that of the sensible heat, and only when the flow ratio is greater than 1 is the latent heat utilization of the 7.11 % PCM emulsion similar to that of the sensible heat.

Analysis of thermal production effect of multi-horizontal U-shaped well

The multi-horizontal section hot dry rock (HDR) heat extraction system is proposed for efficient deep geothermal resources mining in this study. The thermal-hydraulic numerical model of the multi-horizontal section geothermal exploitation system is set up, the space-time evolution of temperature field is analyzed. The sensitivity factors including completion schemes, horizontal well diameter, quantity of horizontal sections and spacing of horizontal sections are investigated. The simulation results show that the production temperature and heating power of the multi-horizontal HDR production system decrease with the development of mining, and the decreasing speed gradually slows down. The open hole completion can be preferred when the formation conditions permit. The variation of horizontal well diameter has little effect on heat production when other conditions remain unchanged. The quantity of horizontal sections to be 3 or 4 for better heat extraction performance under the spacing of horizontal section remains 300m and the spacing of the horizontal section to be 150m is recommended within the scoped of this study. The results of this study can provide guidance for HDR mining research.

Numerical investigation on the thermal performance of a molten salt tank under different electric heating method

Two-tank molten salt (MS) thermal energy storage (TES) technology is an efficient and widely used energy storage technology. This study develops a two-dimensional discrete model (2DIM) using the Modelica language to accurately and quickly represent molten salt temperature distribution and heat loss, applicable to system-level analysis in thermal power systems. It also uncovers variations in heat loss, cooling rate, and required auxiliary electric heating power across different tank volumes, liquid levels, and MS temperatures, offering guidance for optimizing design, energy management, and operational strategies. Additionally, the study examined the impact of different electric heater placements on the performance of the thermal storage system. The results show that heating the gas inside the tank is more effective than traditional direct electric heating, reducing molten salt heat loss by 25.89 % and increasing energy storage efficiency by 0.17 %.The research provide a reference for the study of efficient utilization of TES tank in different thermal systems.

Experimental characterization of leading edge cracking on bulk tungsten divertor components during 2017–2019 WEST operation

During the 2017–2019 WEST operation, a set of ITER-like plasma-facing units consisting of tungsten monoblocks was installed on the lower divertor. Despite modest heating power, 27 % of these monoblocks had cracks on their poloidal leading edges, which were not protected by a toroidal bevel. A comprehensive experimental characterization of the 133 cracked monoblocks indicates that damage occurs near the plasma strike point areas where neat cracks separated by 0.15–0.5 mm in the poloidal direction were observed. Cracks are up to 1 mm long and 1 mm deep and did not affect the lower divertor ability to sustain long pulses. The most important parameter affecting crack formation is the relative vertical misalignment between components.

Application of pressure small signals extraction and amplification technology in abandoned well pattern for geothermal energy extraction and H2 storage: Numerical modeling and economic analysis

Using abandoned reservoirs for geothermal energy development and H2 storage is economical. The impact of complex fractures from long-term oil and gas extraction on geothermal energy and H2 storage is not yet clearly understood. Here, a pressure small signals extraction and amplification (PSEA) technology is developed to improve reservoir monitoring accuracy. This technology is capable of coupling many pressure transient analysis models to invert parameters for multiple scenarios. This work establishes numerical models to simulate the effects of geothermal energy extraction and H2 storage over 5000 days. Results show that this technology improves the accuracy of inverted parameters by 4–14 times. This technology adjusts the production temperature differences in a single injection-production system from 1.4K to 6.5K and the net heat power from 0.25 MW to 1.1 MW, and it can also identify an early low-rate H2 storage phase. The Non-Sorting Genetic Algorithm II calculates that the PSEA technology brings economic benefits of $704,000 and $352,000 for geothermal energy extraction and H2 storage in a single injection-production system. In conclusion, the developed monitoring technology and models improve accuracy in assessing geothermal energy development and H2 storage, preventing failures in residential heating or H2 storage projects.

Heat Transfer Enhancement in a 3D-Printed Compact Heat Exchanger

The study describes experimental data on thermal tests during the condensation of HFE7100 refrigerant in a compact heat exchanger. The heat exchanger was manufactured using the additive 3D printing in metal. The material is AISI 316L steel. MPCM slurry was used as the heat exchanger coolant, and water was used as the reference medium. The refrigerant was condensed on a bundle of circular tubes made of steel with an internal/external diameter of di/de = 2/3 mm, while a mixture of water and phase change materials as the coolant flowed through the channels. Few studies consider the heat exchange in condensation using phase change materials; furthermore, there is also a lack of description of heat exchange in small-sized exchangers printed from metal. Most papers deal with computer research, including flow simulations of heat exchange. The study describes the process of heat exchange enhancement using the phase transition of coolant. Experimental data for the mPCM slurry coolant flow was compared to the data of pure water flow as a reference liquid. The tests were carried out under the following thermal and flow conditions: G = 10–450 [kg m−² s−1], q = 2000–25,000 [W m−²], and ts = 30–40 [°C]. The conducted research provided many quantities describing the heat exchange in compact heat exchangers, including heat exchanger heat power, heat exchange coefficient, and heat exchange coefficients for working media. Based on these factors, the thermal performance of the heat exchanger was described. External characteristics include the value of the thermal power and the heat exchange coefficient as a function of the mass flow density of the working medium and the average logarithmic temperature difference. The performance of the heat exchanger was presented as the dependencies of the heat exchange coefficients on the mass flux density and the heat flux density on the heat exchange surface. The thickness of the refrigerant’s condensate film was also determined. Furthermore, a model was proposed to determine the heat exchange coefficient value for the condensing HFE7100 refrigerant on the outer surface of a bundle of smooth tubes inside a compact heat exchanger. According to experimental data, the calculation results were in good agreement with each other, with a range of 25%. These data can be used to design mini condensers that are widely used in practice.

Scaling up magnetocaloric heat pump for building decarbonization initiatives

Building decarbonization necessitates renewable heating and cooling solutions such as heat pumps. Magnetocaloric heat pumps (MCHP) offer environmental and efficiency advantages but face challenges when scaling up from existing active magnetic regenerator configurations. This study highlights uneven flow resistance, porosity, and refrigerant magnetocaloric effects as key obstacles to MCHP performance in parallel multi-bed setups. To address these effects, two control strategies for the fluid flow control system were investigated: measurement feedback control and model predictive control. Results show a 36.9 % heating power improvement with measurement feedback control, though with extended control convergence times. Model predictive control achieved approximately seven times faster control convergence compared to the measurement feedback control strategy, despite exhibiting minor overshooting. Utilization factor-based model predictive control increased the heating capacity by 1.6 %–30.9 % and the COP by 1.2 %–10.7 % in scenarios with uneven flow resistance and porosity, offering computational efficiency but assuming even magnetocaloric effects between regenerators. This assumption can be addressed by outlet temperature-based model predictive control, albeit at a higher computational cost using genetic algorithm. The findings emphasize the importance of advanced control methods to scaling up MCHP in renewable energy building systems.

Hot gas bypass defrosting with auxiliary heat source in household refrigerators

Frost is inevitable in air-cooled household refrigerators. To maintain the performance of the refrigeration system and food storage quality, additional power input is required to melt the ice periodically. Hot gas bypass defrosting featured high defrosting efficiency, however, suffered insufficient defrosting power at low ambient temperatures, leading to rare application of this technology in household refrigerators. To mitigate this challenge, a novel cost-effective hot gas bypass defrosting system with an auxiliary heater wrapped along the hot gas bypass loop was proposed, and its performance was thoroughly investigated in this paper. Experimental results showed that the defrosting efficiency was 0.8 at an ambient temperature of 32 °C, which was much higher than that of baseline electric defrosting of 0.3. At 20 °C, the new defrosting system with 80 W additional power input in the auxiliary heater successfully melted all frost within 35 min, while the baseline hot gas bypass defrost system without additional heat input could not melt all frost even after 60 min. To further investigate the effects of ambient temperature, compressor speed, and auxiliary heating power, a mathematical model was established and validated by experimental data. The simulated results suggested that it was more efficient to supply more heat from the auxiliary heat source than from the compressor.

Numerical appraisal of the role of heat transfer regimes on transient response of carbon dioxide based supercritical natural circulation loop during power upsurge

Appearance of steep property gradients with change in temperature is a fascinating feature of any supercritical fluid, which can instigate intricate dynamics in supercritical natural circulation loops by modulating the effective forces. While most of the relevant literature focuses on stability evaluation, anticipation regarding the transient response of the system during power transition is of utmost significance, especially in high-power applications. Present study aims at furnishing insight on the same by developing a one-dimensional numerical model of a rectangular loop with supercritical CO2 as the working medium, and characterizing the temporal trends over a wide range of heating power. Two different profiles of power upsurge have been tested for different regimes of heat transfer, unearthing intriguing characteristics. The combination of initial and final regimes during any transformation is found to be the most crucial factor. Single-step rise in power, in general, is the most vulnerable one, specifically during large-scale change of the order of 1000 W, and better be employed only at low-power regime. Even single-step change ∼ 25 W can inflict instability and flow transition within the transition regime. Power transformation following linear ramp profile with transition periods of 5, 10 and 20 s is identified to be the most suitable one across all the regimes. It can successfully mitigate instability even in the later parts of the transition regime, albeit at the expense of greater time requirement to attain the final stable state and possibly a greater period of transformation. Change through multiple small steps (about 250 W for large change in low power regime and 15 W within transition regime) can also be a feasible option for avoiding the growth of unstable oscillations at higher powers.

Experimental studies on the cooling and heating performance of a highly emissive coating

In this study, the cooling effect below ambient air temperature, heat dissipation properties and heating energy efficacy of a superomniphobic self-cleaning (SSC) highly emissive (HE) coating were systematically investigated. Except at midday, the SSC-HE coating with an extremely high solar reflectance of 0.985 showed a better cooling effect than a 10-cm-thick polyurethane insulation layer. The coating substantially reduced the interior air temperature of a well-insulated system by as much as 6.9 °C. The SSC-HE coating enabled the roof surface and room temperatures of the brick bungalow to be 3.4 and 10.2 °C below the ambient air temperature, respectively. Compared with the sunshade and spray water, the SSC-HE coating exhibited better cooling effect. The SSC topcoat allowed the battery cabinet of an HE-coated distributed telecommunication base station to remain its original sub-ambient cooling effect for a long time. Regardless of the location of the HE-coated metal facility, the ultrahigh emissivity of the coating enabled it to exhibit excellent heat dissipation performance during both day and night, even under adiabatic conditions. Additionally, under identical room temperature settings, the HE-coated electric oil heater not only showed faster heating but also had heating energy efficiency of 5.9 % and 4.4 % relative to heaters coated with aluminium- and black paints, respectively. Under identical heating power consumption levels, compared to black paint-coated heater, the HE-coated heater endowed the surrounding environment with a higher equilibrium air temperature, improving the thermal comfort of the indoor environment.

Influence of design parameters on heat production of a multilateral butted closed loop geothermal system

To efficiently develop hot dry rock and other geothermal energy, a multilateral butted closed loop geothermal system (MBCLGS) is presented in this paper to replace the U-shaped closed-loop geothermal system (UCLGS). Besides, a casing-cement-formation transient heat transfer model is established to investigate the influences of key factors on the heat production of MBCLGS. After thermal-fluid-structural coupling analysis, we can find that higher injected rate and lower fluid temperature can improve heat power but reduce output temperature. In addition, the output temperature and heat power do not increase continuously with the increasing of branch well number. There is an optimal value of branch well number. Longer well pair distance can improve both output temperature and heat power. Considering the drilling technology level and design purpose, the recommended injected flow rate of MBCLGS is 90 m3/h, the injected fluid temperature is 42.5 °C, the number of branch wells is 10 and the well pair distance is 200m. Finally, by comparing MBCLGS and UCLGS, it is found that MBCLGS has a lower temperature decline rate and higher output temperature than UCLGS under the same conditions. It works more stable and has better economy. Overall, the proposal of MBCLGS is expected to promote the efficient development of deep geothermal resources.

Impurity behaviour in JET high-current baseline scenario for Deuterium, Tritium and Deuterium-Tritium plasmas

To support future ITER operation, experimental campaigns at the Joint European Torus (JET) with an ITER-like wall (tungsten divertor and beryllium main chamber) in pure deuterium (D), tritium (T) and Deuterium-Tritium (D-T) were performed. One of the most important challenges in recent years was the development of two main scenarios that investigated different approaches to achieve the high fusion power as well as good plasma confinement (Garzotti et al., 2023). The first one, so-called baseline scenario is relying on high plasma current (Ip≈3.5 MA), normalized beta βN < 2 and safety factor q95 ≈ 3 (Garzotti et al., 2023). On the other hand, the second one, so-called Hybrid scenario is operating at lower plasma current (flat-top Ip ≤ 2.6 MA) and density with respect to the baseline, higher normalized beta βN > 2 and safety factor q95 ≈ 4.8 (Hobirk et al., 2023).In this paper we focus on the impurity behaviour analysis for the baseline discharges at Ip = 3.5 MA and BT = 3.3 T with D, T and DT plasmas, in which the gas and power waveform were optimized to achieve the best possible performance. In particular, we study the impact of total heating power (Ptot + Palpha), flat-top gas flow and ELM (edge localized modes) frequency on mid-Z (Nickel (Ni), Copper (Cu)) and high-Z (Tungsten (W)) impurities. In addition, we compared the two best performing pulses of the baseline scenario (Ip = 3.5MA, BT = 3.3 T and Pin ≈ 35 MW) in D and DT in order to identify the causes responsible for the increase in radiation during the DT pulse, which led to an early plasma termination. All presented results rely on the data collected by the VUV as well as the bolometry system. Detailed analysis indicates that in the baseline scenario, higher radiation, which is most likely due to the tungsten (W), is observed for T and DT plasmas in comparison to D. Moreover, for the two best performing baseline pulses, tomographic reconstructions show that the radiated power density is mainly emitted from the low field side (LFS) of the plasma and W does not accumulate in the plasma center (Telesca et al., 2024).

Unraveling conditions for W-shaped interface and undercooled melts in Cz-Si growth: A smart approach

In Cz-Si growth, concave and W-shaped solid–liquid interfaces and undercooled melts are primary contributors to the degradation of crystal quality, particularly structure loss, defect generation, non-uniform dopant distribution, and crystal twisting, making their avoidance crucial. We employed a classification tree machine learning approach to investigate the importance of 15 process and furnace design parameters and their critical ranges for the formation of various types of W-shaped interfaces and undercooled melts at different scales, both in dimensional and dimensionless forms, and across a wide range of process conditions. Moreover, symbolic regression was used to predict minimal melt temperature based on the aforementioned inputs. Training data were obtained by CFD modeling. The classification tree for combined output identified the Grashof, Reynolds for crystal, and Stefan numbers, along with the percentage of silicon solidified, as the most decisive inputs. Symbolic regression for the temperature of undercooled melt highlighted crucible diameter, pulling rate, and the power of the bottom heater as key parameters.

Tri-generation of sensible heat, hydrogen, and electricity in an aluminum-air flow battery (AAB) system

The performance of an aluminum-air flow battery (AAB) unit cell is experimentally studied for application to a tri-generation system as a district heating resource of sensible heat storage, hydrogen production, and electric power generation. A layer-type unit cell is designed to protect against leakage of hydrogen gas during operation and to ensure electrolyte circulation in the AAB system. The electrolyte is made with NaOH pellets dissolved in purified water. A direct current (DC) loader is used to measure the electric power of the AAB unit cell, while a resistance temperature detector (RTD) is used to measure the electrolyte temperature at the unit cell inlet and outlet. The objective of the present work is to study the effect of operation parameters [i.e., electrolyte temperature (Tin), mass flow rate (ṁNaOH), and molar concentration (XNaOH)] on the performance of the tri-generation AAB system. The electric power of the AAB unit cell increases in the electrolyte temperature from 20 ℃ to 50 ℃ with increases in the NaOH molar concentration from 1 M to 4 M. The performance measurement of the AAB unit cell shows that the total surface power density of sensible heat, hydrogen, and electric power increased with increases in electrolyte temperature from 35 ℃ to 55 ℃. The tri-generation system operates for 140 min under the condition of Tin = 40 ℃, ṁNaOH=14.48 g/s, and XNaOH=4 M.

Effects of corrugation on convective heat transfer and power generation in a wavy walled triangular cavity equipped with inclined elastic fin and piezo-energy harvester assembly

Piezoelectric energy harvesters are one of the energy conversion technologies that can be used to convert a variety of external sources, including wind, fluid motion, and vibrations, into electrical energy. This work suggests a novel wall corrugation design in addition to an elastic fin piezo assembly arrangement for power generation and thermal management in a triangular cavity during turbulent forced convection of air. Using the finite element method with ALE, the analysis is conducted for different values of fin inclination (γ between 0 and 60), corrugation amplitude (Af between 0.01H and 0.06H), corrugation frequency (Nf between 1 and 20) and fin distance from the mid-point of the inclined wall in wall direction. The average Nusselt number (Nu) and generated power (PW) show a non-linear increasing trend with increasing fin tilt. Average Nu increment factor becomes 5.17 with the highest fin inclination while the power increments become 11.6 and 4.46 when rising inclination from 30 to 45 and from 45 to 60. The generated power rises with higher corrugation amplitude and wave number. However, increasing the wave number results in thermal performance degradation. Increment of average Nu becomes 1.17 with highest corrugation amplitude while it declines by a factor of 10.3 at the highest wave number. Power enhancement factors of 5.73 and 2.32 are obtained by increasing the corrugation amplitude from Af = 0.0714H to Af = 0.1786H and from Af = 0.1786H to Af = 0.2143H. When fin positions sf = 0.7143H and sf = -0.7143H are compared with the case of fin location at sf = 0, the power increment factors become 12.27 and 4.76, respectively. For the power produced by the piezo device, a polynomial type correlation is suggested by adjusting the parameters of the corrugated wall.

A comparative study of Fibre Bragg Grating for spatially and temporally resolved gas temperature measurements in cold atmospheric pressure plasma jets

Abstract Cold atmospheric pressure plasma jets (CAP-Jet) are successfully used in medical ther-apy for healing of chronic wounds and are widely researched in inactivation of patho-gens and in assisting in cancer therapy. A crucial parameter for these plasma applica-tions is that CAP-Jets operate at temperatures that are tolerable for biological tissues. While tools characterizing the plasma's gas temperature are well developed, there are only a few methods that work with an agreeable limit of uncertainty, complexity and limited perturbation properties to accurately determine that the studied plasma jet operates at tissue tolerable temperatures at all times. In the current work, time resolved measurements of the gas temperature in the effluent of a CAP-Jet are performed using the innovative technique of a Fibre Bragg Grating (FBG), in which the temperature dynamics is measured by a shift of the FBGs resonant wavelength through its thermo-optic coefficient. Comparing with other temporal and spatial diagnostic tools such as thermocouple measurement, Schlieren imaging, and optical emission spectroscopy, we demonstrate reliable calorimetric measurements at different plasma duty cycles. The plasma source maintains tissue tolerable temperatures inside the plasma active zone with values below 35°C at 1 cm distance from the jet nozzle. The calorimetric measure-ments have revealed that the heat power dissipation in comparison to electric energy of our plasma source is at least 50%.