Low Heating Power Research Articles

Experimental study on combined buoyant-thermocapillary flow along with rising liquid film on the surface of a horizontal metallic mesh tube

Temperature distribution and variation with time has been considered in the analysis of the influences of the initial level of immersion of a horizontal metallic mesh tube in the liquid on combined buoyant and thermocapillary flow. The combined flow occurs along with the rising liquid film flow on the surface of a horizontal metallic mesh tube. Three different levels of immersion of the metallic mesh tube in the liquid have been tested. Experiments of 60 min in duration have been performed using a heating metallic tube with a diameter of 25 mm and a length of 110 mm, sealed outside with a metallic mesh of 178 mm by 178 mm, and distilled water. These reveal two distinct flow patterns. Thermocouples and infrared thermal imager are utilized to measure the temperature. The level of the liquid free surface relative to the lower edge of the tube is measured as angle θ. The results show that for a smaller θ angle, or a low level of immersion, with a relatively low heating power, it is possible to near fully combine the upwards buoyant flow with the rising liquid film flow. In this case, the liquid is heated only in the vicinity of the tube, while the liquid away from the flow region experiences small changes in temperature and the system approaches steady conditions. For larger θ angles, or higher levels of immersion, a different flow pattern is noticed on the liquid free surface and identified as the thermo-capillary (Marangoni) flow. The rising liquid film is also present. The higher levels of immersion cause a high temperature gradient in the liquid free surface region and promote thermal stratification; therefore the system could not approach steady conditions.

Investigation of Rapid Low-Power Microwave-Induction Heating Scheme on the Cross-Linking Process of the Poly(4-vinylphenol) for the Gate Insulator of Pentacene-Based Thin-Film Transistors.

In this study, a proposed Microwave-Induction Heating (MIH) scheme has been systematically studied to acquire suitable MIH parameters including chamber pressure, microwave power and heating time. The proposed MIH means that the thin indium tin oxide (ITO) metal below the Poly(4-vinylphenol) (PVP) film is heated rapidly by microwave irradiation and the heated ITO metal gate can heat the PVP gate insulator, resulting in PVP cross-linking. It is found that the attenuation of the microwave energy decreases with the decreasing chamber pressure. The optimal conditions are a power of 50 W, a heating time of 5 min, and a chamber pressure of 20 mTorr. When suitable MIH parameters were used, the effect of PVP cross-linking and the device performance were similar to those obtained using traditional oven heating, even though the cross-linking time was significantly decreased from 1 h to 5 min. Besides the gate leakage current, the interface trap state density (Nit) was also calculated to describe the interface status between the gate insulator and the active layer. The lowest interface trap state density can be found in the device with the PVP gate insulator cross-linked by using the optimal MIH condition. Therefore, it is believed that the MIH scheme is a good candidate to cross-link the PVP gate insulator for organic thin-film transistor applications as a result of its features of rapid heating (5 min) and low-power microwave-irradiation (50 W).

Two-Phase Closed-Loop Thermosyphon Solar Water Heater with Porous Wick Structure: Performance and Start-Up Time

Two-phase closed-loop thermosyphons (TPCLTs) are highly efficient heat transfer devices capable of transporting thermal energy over long distances without the need for other mechanical forces, such as pumPWS. This makes TPCLTs particularly suitable for applications involving solar water heaters. Our objective in this work was to increase the performance of TPCLT solar water heaters by using an evaporator with a porous wick structure (PWS) to achieve a low heat transfer coefficient. Experiments were conducted under three conditions: (1) 40% fill ratio using an evaporator without a PWS, (2) 60% fill ratio using an evaporator without a PWS, (3) 60% fill ratio using an evaporator with a PWS. Our results demonstrate that employing a PWS within the evaporator can enhance efficiency by 12.7% and decrease start-up time by 26.5% under low heating power.

An Investigation on Eddy Current Pulsed Thermography to Detect Surface Cracks on the Tungsten Carbide Matrix of Polycrystalline Diamond Compact Bit

Polycrystalline diamond compact (PDC) bits are commonly used drill bits in the petroleum drilling industry. Cracks often occur on the surface of a bit, which may result in the unexpected suspension of the drilling operation, or even accidents. Therefore, the detection of surface cracks on PDC bits is of great importance to ensure continuous drilling operation and to prevent accidents. However, it is extremely difficult to detect such cracks by visual inspection or other traditional nondestructive testing (NDT) techniques due to the small size of cracks and the irregular geometry of bits. As one emerging NDT technique, eddy current pulsed thermography (ECPT) can instantly detect surface cracks on metal parts with irregular geometry. In this study, the feasibility of ECPT of detecting surface cracks on the tungsten carbide matrix of PDC bits was investigated. A successive scanning detection mode is proposed to detect surface cracks by using ECPT with a low power heating excitation unit and small-size coils. The influence of excitation duration on the detection result was also investigated. In addition, principal component analysis (PCA) was employed to process the acquired IR image sequences to improve detection sensitivity. Finally, the whole shape of a crack was restored with processed images containing varied cracks segments. Based on the experimental results, we conclude that the surface cracks on the tungsten carbide matrix of PDC bit can be detected effectively and conveniently by ECPT in scanning mode with the aid of PCA.

Experimental investigation of heat transfer and pressure drop in a straight minichannel heat sink using TiO2 nanofluid

In this paper, heat transfer and pressure drop characteristic associated with minichannel heat sink is investigated experimentally. TiO2 nanofluid with 15% weight concentration in water as base fluid is used as a coolant and its performance is compared with the distilled water at heating powers of 100W, 125W and 150W. The results indicate that TiO2 nanofluid thermal performance is strongly dependent on heating power and its usefulness heat transfer characteristic could be achieved more effectively at lower heating power. However, pressure drop is found to increase with the decrease of heating power and this decrement is more prominent for TiO2 nanofluid as compared to distilled water due to viscosity variation with temperature. Nusselt number is found invariant with increase or decrease of heating power and hence using distilled water, experimental Nusselt number satisfies Peng and Peterson empirical correlation at all heating powers within 20% accuracy. The lowest wall temperature is measured to be 37.05°C using TiO2 nanofluid at Reynolds number of 922 corresponding to heating power of 100W. Moreover, while passing through the minichannel, an axial rise of base temperature is observed from inlet to outlet of heat sink.

Innovative heating of large-size automotive Li-ion cells

Abstract Automotive Li-ion cells are becoming much larger and thicker in order to reduce the cell count and increase battery reliability, posing a new challenge to battery heating from the cold ambient due to poor through-plane heat transfer across a cell's multiple layers of electrodes and separators. In this work, widely used heating methods, including internal heating using the cell's resistance and external heating by resistive heaters, are compared with the recently developed self-heating Li-ion battery (SHLB) with special attention to the heating speed and maximum local temperature critical to battery safety. Both conventional methods are found to be slow due to low heating power required to maintain battery safety. The heating power in the external heating method is limited by the risk of local over-heating, in particular for thick cells. As a result, the external heating method is restricted to ∼20 min slow heating for a 30 °C temperature rise. In contrast, the SHLB is demonstrated to reach a heating speed of 1–2 °C/sec, ∼40 times faster for large-size thick cells, with nearly 100% heating efficiency and spatially uniform heating free from safety concerns.

Effects of different excitation waveforms on detection and characterisation of delamination in PV modules by active infrared thermography

Delamination significantly affects the performance and reliability of photovoltaic (PV) modules. Recently, an active infrared thermography approach using step heating has been exploited for the detection and characterisation of delamination in PV modules. However, step heating takes longer observation time and causes overheating problems. This paper presents the effects of different thermal excitation waveforms namely rectangular, half-sine and short pulse, on the detection and characterisation of delamination in PV module by experiments and simulations. For simulation, a 3-dimensional electro-thermal model of heat conduction, based on resistance-capacitance network approach, has been exploited to study the variation in maximum thermal contrast and peak contrast time with the delamination thickness and heating parameters. Results show that the rectangular waveform provides better detection of delamination due to higher absolute contrast, while the half-sine waveform allows better characterisation of delamination in the PV modules with low-cost and low-power heat source. The high-energy short pulse enabled quick visualisation of delamination, but has limited practical implementation. The advantages and limitations of each waveform have been highlighted to assess the specific requirement for appropriate choice in the non-destructive thermographic inspection of delamination in PV modules at the manufacturing units or outdoor fields.

Development of the Q = 10 scenario for ITER on ASDEX Upgrade (AUG)

The development of the baseline H-mode scenario foreseen for ITER on the ASDEX Upgrade tokamak, i.e. discharges at q95 = 3, relatively low βN ~ 1.8, high normalized density n/nGW ~ 0.85 and high triangularity δ = 0.4, focused on the integration of elements foreseen for ITER and available on ASDEX Upgrade, such as ELM mitigation techniques and impurity seeding in combination with a metallic wall. Values for density and energy confinement simultaneously came close to the requirements of the ITER baseline scenario as long as βN stayed above 2. At lower heating power and thus lower βN normalized energy confinement H98y2 ~ 0.85 is obtained. It has been found that stationary discharges are not easily achieved under these conditions due to the low natural ELM frequency occurring at the low q95/high δ operational point. Up until now the ELM parameters were uncontrollable with the tools developed in other scenarios. Therefore studies on an alternative operational point at higher βN and q95 have been conducted. In order to prepare for the ITER first non-activation operational phase, Helium operation has been investigated as well.

COREDIV and SOLPS Numerical Simulations of the Nitrogen Seeded JET ILW L‐mode Discharges

AbstractIn this paper we present the comparison of simulations with the numerical codes COREDIV and SOLPS5.0 for JET L‐mode discharges with ITER like wall (ILW). The simulations have been performed for L‐mode shots with and without nitrogen seeding (#82291 ‐ 9) which are characterised by relatively low auxiliary heating power (PNBI = 1.1 MW) and low electron density (ne = 2.35 × 1019 m–3). Comparisons are made to the experimental measurements (e.g. radiation levels, plasma profiles) and the differences between the results from the two codes (e.g. temperature and density profiles at the outer divertor plate) are shown and discussed.

Experimental investigations on flow characteristics of two parallel channels in a forced circulation loop with supercritical water

The instability of supercritical water flow inside two parallel channels is investigated experimentally in this paper. Two types of instabilities with various oscillation periods occur at different power region during the heating process, indicating the existence of two types of dynamic instabilities. The type I instability occurs when the outlet temperature of the test section surpasses the pseudo-critical temperature. Sudden increase of the pressure drop cause a big disturbance to the system which results in a periodic feedback between the pressure drop and the mass flow rate. Large oscillations were found in the entire system at low heating power during which the two parallel channels oscillates in phase with the whole system with a long oscillation period (20–300s). The type II instability occurs only in the heated section at high powers at which the two parallel channels oscillate 180° out of phase while the rest of the system is stable. The period of type II instability is relatively small, i.e. 2–5s. With Ambrosini’s non-dimensional parameters, a stability map was generated using the obtained instability data. Analysis of the instability map showed the expected result that no instability occurs when the exit fluid temperature is below the pseudo-critical temperature regardless of the system pressure, inlet temperature, heating power, and local loss coefficient. The influences of inlet mass flow rate, inlet fluid temperature and system pressure on instabilities were also studied.

Method of calculating heat transfer in furnaces of small power

This publication presents the experiences and results of generalization criterion equation of importance in the analysis of the processes of heat transfer and thermal calculations of low-power heat generators cooled combustion chambers. With generalizing depending estimated contribution of radiation and convective heat transfer component in the complex for the combustion chambers of small capacity boilers. Determined qualitative and quantitative dependence of the integrated radiative-convective heat transfer from the main factors working combustion chambers of small volume.

EFFECT OF WORKING FLUID, FILLING RATIO AND NUMBER OF TURNS ON PULSATING HEAT PIPE THERMAL PERFORMANCE

Pulsating heat pipe’s (PHP) are one of the alternatives to conventional heat transfer technologies. First part of this paper, titled: thermohydrodynamic behavior of methanol charged closed loop pulsating heat pipe has given information about thermo-hydrodynamic operational characteristics such as; bubble nucleation and collapse, bubble agglomeration and pumping action, flow regime changes, pressure/temperature perturbations, dynamic instabilities, meta-stable non-equilibrium conditions etc. in the PHP. Present paper, which is an extension of the previous work, it presents some more thermal results to highlight the effect of; thermo-physical properties of working fluid, filling ratio and number of turns on thermal performance of PHP. Three different PHP loop has been made from six, four and two parallel glass tubes (i.e. three turns, two turns and one turn at evaporator section) forming adiabatic section, interconnected alternately by copper U tubes, having internal and external diameter 2 mm and 3.06 mm respectively. The length of evaporator, condenser and adiabatic section are 42 mm, 50 mm and 170 mm respectively. The experimentation conducted for different working fluids (water, ethanol, methanol and acetone), different filling ratio’s (30%FR, 50%FR and 70%FR) and different number of turns (one, two and three turns). The motto of present research is to understand the thermal performance in terms of thermal resistance of PHP in details. The result shows that, thermal resistance for all working fluid PHP’s rapidly decreases with increasing heating power up to 32W. For low heating power, working fluid (acetone) which has lower boiling temperature is best, but it cannot give the service for higher heating power. Two turn PHP loop with methanol 50% volumetric filling ratio at more than 32W heating power with one directional flow circulation is the optimum operating condition of present research.

Optimization of the Efficiency of Steam Electrolysis and Co-Electrolysis to Produce Methane According to Heat Power Recovery

Among potential energy storage solutions, many require the development of major infrastructures (hydraulics sites, subterranean cavities, hydrogen storage systems). That is why, more recently, the carbon-free electricity storage into synthetic fuels is of increasing interest, representing an alternative with great potential called "Power to gas ". The manufacture of a synthetic fuel from water, carbon dioxide and carbon-free electricity meets a number of objectives for overall efficiency improvement: - Reducing CO2 emissions from fossil fuel use, - offering CO2 reuse rather than storing it for an indefinite period, - Turning all carbon-free electrical sources (renewable and nuclear), especially during periods of overproduction into a storable product, with the possibly of regenerating electricity during periods of production deficits. In this perspective of reducing CO2 emissions, High Temperature Steam Electrolysis (HTSE) is a promising way to produce massively hydrogen. This process operates at high temperatures (> 700 ° C). The operating conditions with vapor and high temperature reduce the amount of consumed electrical energy by the electrolysis reaction. This has to be realized by increasing the thermal energy part, coming from cheap sources. In addition, this high temperature based technology allows either solid oxide electrolysis of H2O steam to produce H2 and / or co-electrolysis of H2O + CO2 which produces syngas (H2 + CO), paving the way for the production of hydrocarbons including methane. Producing synthetic natural gas then gives the possibility of using immediately all existing infrastructures: transmission and distribution, storage capacity, power generation facilities, etc ... This technology offers very high performance by lowering the amount of electricity required, provided high level of heat recovery, especially to vaporize the water. Here are presented schemes involving several processes with high temperature electrolysis or co-electrolysis technology coupled with a catalytic CO2 or CO hydrogenation reactor. This type of reactors is highly exothermic. Therefore a thermal integration is proposed but an external heat source should also be added, modifying the process schemes. For a power and a level of available heat source temperature, the several schemes to produce methane are therefore optimized and compared according to their efficiencies, produced methane quality, heat recovery and recycled CO2 amount. Moreover for both electrolysis and co-electrolysis, this work provides real operating points for the electrolysis step [1-2], such as voltage, current, possible steam conversion, gas composition, pressure level …etc. The considered catalytic reactor is a Gibbs one. It is shown that in case of low available external heat power, the co-electrolysis mode can offer the best efficiency. Moreover, the co-electrolysis Area Specific Resistance (ASR) is found experimentally close to the steam electrolysis one, leading to a limited impact on the required electrochemical surface. These results confirm the potential of this technology to store the carbon-free electricity: very high efficiencies thanks to the high temperature operation and a very promising help to recycle the CO2 into synthetic fuels. [1] J. Laurencin et al., 2011, Journal of Power Sources, 196, 2080-2093.[2] J. Aicart et al, 2014, Fuel Cells, Vol.14, 3, 430-447 Figure 1

Dynamical model parameter adjustments in model predictive filtering MR thermometry

In magnetic resonance guided focused ultrasound (MRgFUS) brain applications the fully insonified field-of-view (FOV) is ideally monitored. This can be achieved by k-space subsampling and using a dedicated reconstruction method, such as the previously described model predictive filtering (MPF) method.[1] MPF utilizes the Pennes Bioheat transfer equation (PBTE) and tissue thermal and acoustic properties determined from a low-power pre-treatment heating (which ideally does not deliver any thermal dose, i.e. ΔT<2°C). The accuracy of the determined tissue parameters, and hence of the MPF reconstruction, depends on the low power heating. In this work we investigate dynamical adjustment of model parameters during heating for improved MPF temperature measurement accuracy.

Recent ASDEX Upgrade research in support of ITER and DEMO

Recent experiments on the ASDEX Upgrade tokamak aim at improving the physics base for ITER and DEMO to aid the machine design and prepare efficient operation. Type I edge localized mode (ELM) mitigation using resonant magnetic perturbations (RMPs) has been shown at low pedestal collisionality . In contrast to the previous high ν* regime, suppression only occurs in a narrow RMP spectral window, indicating a resonant process, and a concomitant confinement drop is observed due to a reduction of pedestal top density and electron temperature. Strong evidence is found for the ion heat flux to be the decisive element for the L–H power threshold. A physics based scaling of the density at which the minimum PLH occurs indicates that ITER could take advantage of it to initiate H-mode at lower density than that of the final Q = 10 operational point. Core density fluctuation measurements resolved in radius and wave number show that an increase of R/LTe introduced by off-axis electron cyclotron resonance heating (ECRH) mainly increases the large scale fluctuations. The radial variation of the fluctuation level is in agreement with simulations using the GENE code. Fast particles are shown to undergo classical slowing down in the absence of large scale magnetohydrodynamic (MHD) events and for low heating power, but show signs of anomalous radial redistribution at large heating power, consistent with a broadened off-axis neutral beam current drive current profile under these conditions. Neoclassical tearing mode (NTM) suppression experiments using electron cyclotron current drive (ECCD) with feedback controlled deposition have allowed to test several control strategies for ITER, including automated control of (3,2) and (2,1) NTMs during a single discharge. Disruption mitigation studies using massive gas injection (MGI) can show an increased fuelling efficiency with high field side injection, but a saturation of the fuelling efficiency is observed at high injected mass as needed for runaway electron suppression. Large locked modes can significantly decrease the fuelling efficiency and increase the asymmetry of radiated power during MGI mitigation. Concerning power exhaust, the partially detached ITER divertor scenario has been demonstrated at Psep/R = 10 MW m−1 in ASDEX Upgrade, with a peak time averaged target load around 5 MW m−2, well consistent with the component limits for ITER. Developing this towards DEMO, full detachment was achieved at Psep/R = 7 MW m−1 and stationary discharges with core radiation fraction of the order of DEMO requirements (70% instead of the 30% needed for ITER) were demonstrated. Finally, it remains difficult to establish the standard ITER Q = 10 scenario at low q95 = 3 in the all-tungsten (all-W) ASDEX Upgrade due to the observed poor confinement at low βN. This is mainly due to a degraded pedestal performance and hence investigations at shifting the operational point to higher βN by lowering the current have been started. At higher q95, pedestal performance can be recovered by seeding N2 as well as CD4, which is interpreted as improved pedestal stability due to the decrease of bootstrap current with increasing Zeff. Concerning advanced scenarios, the upgrade of ECRH power has allowed experiments with central ctr-ECCD to modify the q-profile in improved H-mode scenarios, showing an increase in confinement at still good MHD stability with flat elevated q-profiles at values between 1.5 and 2.

Personal environmental control: Effects of pre-set conditions for heating and lighting on personal settings, task performance and comfort experience

The effects of pre-set environmental conditions of temperature and lighting on the preferred personal settings, comfort experience and task performance of office workers were investigated in an individually controlled workstation. Twenty subjects performed standardized tasks at a prototype workstation with individually controlled radiant heating and lighting in a climate room. In a repeated measures design, their adjustments to pre-set values were evaluated: low and high radiant heating power, low and high direct illuminance, low and high indirect illuminance. Results showed that preferred personal settings are dependent on the initial, pre-set values of radiant heating power and illuminance. Higher pre-set values result in higher adjusted operative temperatures and higher illuminances on desk, although the differences for heating were too small to show a convincing effect. After adjustment, visual comfort was higher, but it was not dependent of the pre-set values. For thermal comfort no differences were found. Individual task performance was not negatively affected. Providing personal environmental control and the way these concepts and interfaces are designed, play a significant role in user behavior and preferences. The design and control of individually controlled workstations as well as the interaction with the general level of the office environment should be carefully considered in order to obtain maximum comfort and energy efficiency.

Effects of heating power on divertor in-out asymmetry and scrape-off layer flow in reversed field on Experimental Advanced Superconducting Tokamak

The dependence of divertor asymmetry and scrape-off layer (SOL) flow on heating power has been investigated in the Experimental Advanced Superconducting Tokamak (EAST). Divertor plasma exhibits an outboard-enhanced in-out asymmetry in heat flux in lower single null configuration for in reversed (ion ∇B drift direction toward the upper X-point) field directions. Upper single null exhibits an inboard-favored asymmetry in low heating power condition, while exhibits an outboard-favored asymmetry when increasing the heating power. Double null has the strongest in-out asymmetry in heat flux, favoring the outer divertor. The in-out asymmetry ratios of qt,out/qt,in and Pout/Ptotal increase with the power across the separatrix Ploss, which is probably induced by the enhanced radial particle transport due to a large pressure gradient. The characteristics of the measured SOL parallel flow under various discharge conditions are consistent with the Pfirsch-Schlüter (PS) flow with the parallel Mach number M∥ decreasing with the line averaged density but increasing with Ploss, in the same direction as the PS flow. The contributions of both poloidal E×B drift and parallel flow on poloidal particle transport in SOL on EAST are also assessed.

The Influence of Induction Heating to Remelting Temperature Radial Distribution

The second remelt is an important influencing factor during semi-solid thixotropy forming technology, and the microstructure is immediately impacted by temperature distribution state. By the way of induction heating the temperature distribution state of 45# steel is researched in this paper. The results indicate: the temperature rises slowly by low power heating and the radial temperature distribution doesn’t reach uniform. But the temperature rises rapidly by high power heating and the radial temperature distribution is nearly homogeneous after a while.

Estimation of trial parameters for Pulse Phase Thermography with low power heat sources

Non-destructive Testing by Infrared Thermography (IR-NDT) is a widely adopted technique to reveal the presence of defects, i.e. discontinuity zones of thermal proprieties, inside materials. Pulsed Phase Thermography (PPT) is one of the most interesting techniques among IR-NDT: the specimen is heated by a thermal pulse and the sequence of thermograms of the surface cooling is transformed with the Discrete Fourier Transform (DFT). The resulting phase images (phasegrams) show little sensitivity to irregular heating and surface proprieties, and allow better defect identification by increasing the contrast. It is also possible to estimate the depth of the defect by correlating a characteristic frequency to the thermal diffusion length of the defect. The outcome of this analysis depends on the fine tuning of the technique and the appropriate choice of the parameters of the thermal pulse, namely length and power, as well as of the acquisition: frequency and observation time. While there are in literature a few guidelines for the choice of these parameters, a good knowledge of the technique and a certain degree of guessing is still required, especially when low heating power, longer pulses and small and deep defects are involved. This paper reports a method to estimate these parameters, partly based on theoretic considerations and partly on numerical simulations performed by means of a FEM commercial code on a 2D axial-symmetric model. Experimental results are also here presented, focusing on the difference between a thick plate and a thin one.

Design and dynamic behaviour of a cold storage system combined with a solar powered thermoacoustic refrigerator

A heat powered thermoacoustic refrigerator consists in a thermoacoustic engine that produces acoustic work utilizing heat, coupled to a thermoacoustic cooler that converts this acoustic energy into cooling effect. These machines have already proved their capability in laboratory or in space refrigeration. Previous studies have also demonstrated the possibility of using concentrated solar energy as thermal energy sources for low power heat driven thermoacoustic refrigerators. As other solar refrigeration systems, even if the cooling demand generally increases with the intensity of the solar radiation, one of the major difficulties is to insure a frigorific power supply when there is no, or low, solar radiation. The aim of this work is to study a kW scale solar thermoacoustic refrigerator capable to reach temperatures of the industrial refrigeration domain. This refrigerator is combined with a latent cold storage in order to guarantee a sufficient cooling capacity to face to refrigeration loads in spite of the production fluctuations. A description of the studied prototype is done and the model developed to describe the transient behaviour of the main components of this machine is introduced. The results obtained with a simulation of one week with real solar radiations are presented and the behaviour and the energetic performances of the entire system are analysed. Finally the impact of the sizing of the cold storage system is discussed. With the best storage design, the system is capable to supply a cooling power of 400 W at a temperature equal or lower than −20 °C with an average Coefficient Of Performance of the solar thermoacoustic refrigerator equal to 21%.