Varying Heat Loads Research Articles

Potential of thermosyphon for passive cooling of nuclear fuel storage vault

This study evaluates the potential of thermosyphon for passive cooling of nuclear fuel storage vaults. For this work, a thermosyphon was specifically designed and manufactured. Experiments were conducted by varying heat load (300–600 W) and filling ratio (40–120 %). Optimal performance was obtained with a 60 % filling ratio. The experimental data obtained with the optimal filling ratio were used to calculate the effective thermal conductivity of thermosyphon and determine the number of thermosyphons needed for the vault. Two geometric vault ventilation models; one featuring a thermosyphon and the other without these were developed. The operations of these vault ventilation systems were simulated using the CFD model. The airflow patterns and temperature distributions within the storage vault were compared. The findings ascertain the utility of thermosyphons as an effective passive cooling device in the nuclear fuel storage vault.

Experimental characterisation and visualisation of a novel two-phase flexible heat transfer device

The importance of passive Flexible Heat Transfer Device (FHTD) in electronic cooling or space applications lies in their ability to provide efficient, reliable, and adaptable thermal management solutions. Heat transfer enhancement studies pertaining to FHTD developed to meet the thermal management demands of futuristic flexible electronic devices are presented in the current work. The possibility of extending the heat transport limit of FHTD beyond 24 W by limiting the maximum operating temperature to 60 °C is discussed. The superior performance of FHTD at varying heat loads from 5 W to 40 W at 45°and 90°bending angles is brought out compared with existing heat transfer devices like Flexible Heat Pipe (FHP) and copper thermal straps. The performance is reported in thermal resistance and equivalent thermal conductivity. A commercial dielectric liquid is used as a working fluid in FHTD to enhance the heat transfer limit employing phase change. The evaporator and condenser sections of the flexible section are made transparent to visualise the boiling and condensation phenomenon. Under steady-state operation at a 45°bending angle, The FHTD demonstrates a minimum thermal resistance of 0.73 K/W and a peak effective thermal conductivity of 8172 W/m K. The heat transfer coefficient ranges from 200 to 700 W/m2 K, consistent with values reported for heat pipes in the literature. Additionally, the study explores the impact of modifying the external surface texture to create more nucleation sites, thereby enhancing the performance of the FHTD. The results show that the laser-textured surface on the heat pipe condenser effectively reduces the onset of nucleate boiling for dielectric fluid by 3.5 °C and decreases the maximum temperature of the evaporator by 4.5 °C. The present work dictates the fundamental baseline for possible design choices of futuristic passive flexible heat transfer devices.

Ultra-low temperature heating system based on dual-source solar assisted heat pump using compound parabolic concentrator-capillary tube solar collector

The fifth-generation heating – ultra-low temperature heating benefits to reduce electricity consumption and achieve the net zero goal. The dual-source solar assisted heat pump based heating system has been demonstrated to be an attractive green heating technology for the domestic sector. However, the slower response speed of the low temperature heating to the variation of heating load in responding to the variations of weather conditions limits its thermal comfort performance. The enhancement in solar collector performance brings valuable improvements in response speed of the heating system. In the present work, a heating system based on solar assisted air source heat pump using a compound parabolic concentrator-capillary tube solar collector (CPC-CSC) is investigated with the set heating temperatures of 40, 45, 50, and 55 °C. This heating system works for both space heating and hot water under the weather conditions in London. The results suggest that using a concentrated solar collector improves the response speed of the heating system at low set heating temperatures. For such a heating system, the ultra-low heating temperature increases the application of renewable energy and passive heating (by 6.4%). Compared with the dual-source indirect expansion solar assisted heat pump using flat plate collector, the heating system using CPC-CSC can reduce TEWI by 4.6% with a slightly longer (1.9%) payback period. As the set heating temperature decreases from 55 to 40 °C, the seasonal and yearly system seasonal performance factors significantly increase by 17.1% and 20.5%, respectively.

Dynamic analysis for ultra-supercritical boiler water wall considering uneven heat flux distribution and combustion instability

The dynamic characteristics of water-cooled wall are of great significance to the evaluation of the safety and flexibility for the boiler during peak shaving process. However, few dynamic studies considered the uneven heat flux distribution on the water-cooled wall, let alone the variable heat load caused by the combustion instability. In this paper, a segmented dynamic model is developed for the water-cooled wall of a 660 MW ultra supercritical boiler. The model is validated under steady and dynamic working conditions, respectively. Then, the step responses of the steam temperature in different flow loops under different load conditions are comparatively studied under the disturbances of single-parameter changes. In the cases of 10 % step decrease of either the feedwater temperature, the heat load or the feedwater mass flowrate, the outlet steam temperature is influenced greatly by the step decreased feedwater temperature under 100 % BMCR condition, while it is impacted most by the step decreased feedwater mass flow under 50 % THA condition. Under these disturbances, the outlet steam temperature of the tube with higher heat loads has larger variation and longer response time. In addition, the simulated combustion instability by the sinusoidal fluctuating heat load on the water wall is employed to explore the influences of the flame fluctuation amplitude and frequency to the water wall. The maximum steam temperature rises with the increase in amplitude but drops with the frequency of flame fluctuation. The thresholds for the flame fluctuation amplitude and frequency are obtained under different load conditions.

Thermal performance of a novel hybrid heat pipe with composite heat transfer characteristics

Considering the capillary threshold of oscillating heat pipes (OHP), a novel hybrid heat pipe (HHP) was designed with channels with hydraulic diameters that alternately exceed and fall below this threshold, parallelly arrayed within a unified copper substrate. This technology attains a comprehensive heat transfer performance within the HHP, seamlessly transitioning from pure phase change heat transfer to hybrid pulsating flow heat transfer to effectively accommodate the escalating demands of heat load. Performance and visualization are used to analyze the operational characteristics of HHP. The results indicate that the HHP mainly transfers heat through the phase change in the large channels in lower heat input, while the working fluid in the small channels remains calm. Once the heat input is sufficient, the geyser boiling in the large channels and the liquid slug pulsating in the small channels jointly carry out heat transfer. Furthermore, the liquid content in the large and small channels can be adaptively adjusted to each other. The high-speed liquid in the small channels can be squeezed into the large channels to ensure the sufficient pulsating space and achieve efficient heat transfer under high heat input. In addition, the operation of the HHP can be significantly impacted by the filling ratio (FR). In the phase change stage, the FR of 47.6 % can be considered as the turning point. After transitioning to the hybrid pulsating flow stage, the HHP with low FR can get a better performance. This new type of heat pipe with gradually changing operation characteristics may be critical to solve thermal problems in variable heat load domain.

Dynamic simulation of ITER cryo-distribution system using Aspen HYSYS

The ITER cryogenic system consists of the Liquid Helium (LHe) plant, the Cryo-Distribution (CD) system, and the cryo-lines. The Auxiliary Cold Boxes (ACBs) dedicated to cooling the superconducting (SC) magnet system and the Cryoplant Termination Cold Box (CTCB) of the ITER CD system are in the factory acceptance phase. The internal components of ACBs, e.g., cryogenic valves, a cold compressor (CCp), heat exchangers, and a cold circulator (CCr), have been sized and assembled, ensuring their functionality. The interdependency of the functional parameters of one component over the others needs to be assessed, as their integrated performance under the dynamic heat load deposition from the SC magnets may impact the overall operation of the ITER cryogenic system. The ACBs are equipped with two helium baths having ∼ 1200 kg of He inventory and situated inside the Tokamak building. These baths act as a thermal buffer for the LHe plant, situated in the cryoplant building, allowing it to operate at a quasi-steady state despite heat load variation from the applications. Such a large helium inventory can challenge the secondary confinement system of ITER due to helium ingress accidental events and thus needs to be optimized. The integrated system-level simulation is therefore necessary for the safe and reliable operation of the cryogenic system under such demanding requirements. The present study summarizes the results obtained for ACBs dedicated to the magnet system, including CTCB for the enhanced ITER operation modes, and confirms the integrated performance of the system. The results show that the LHe baths inside the ACBs can be used as a thermal buffer with the proposed limit of initial filling and by keeping a constant opening of the respective J-T valves upstream of the LHe baths. The study outcome and the proposed recommendations would be beneficial to mitigate the pulsed heat load to the LHe plant while minimizing the helium inventory.

Insights into two-phase flow dynamics in closed-loop pulsating heat pipes utilizing Fe3O4/water: experimental visualization study

This article discusses a focused study on visualizing the flow patterns in a two-phase pulsating heat pipe (PHP) using Fe3O4/water as the working fluid at 3 V/V% concentration. The research also aims to meticulously examine phase change phenomena in the heating section, particularly focusing on bubble formation and expansion processes. A high-speed video camera was utilized to capture dynamic insights into the behavior of the Fe3O4/water mixture. Based on the findings, a straightforward model was developed to explain bubble generation and growth in the mixture, serving as a useful reference for future PHP designs and optimizations. Visual observations also noted the stable nature of the Fe3O4/water nanofluid over a 4-day period, confirming its consistency throughout the experiments. Moreover, the impact of heat load variation on the evaporator section was assessed using controlled heat inputs ranging from 10 to 80 W. Observations on the arrangement of slugs and plugs at a 50% filling ratio revealed interesting self-adjusting flow patterns in response to increasing heat inputs, providing valuable insights into PHP operational dynamics. Notably, the oscillatory flow behavior of Fe3O4/water, the chosen working fluid, exhibited greater activity in comparison to water. This distinctive flow behavior contributed to achieving heightened thermal performance efficiency for the Fe3O4/water system, attributed to its faster attainment of the annular flow condition.

Study of Heat Transfer Characteristics of Heat Pipe Using Water as a Working Fluid

Heat pipes are efficient and versatile thermal management devices widely used in various applications to transfer heat. This study focuses on investigating the heat transfer characteristics of a heat pipe employing de-ionized water as the working fluid. The experiment involved analyzing the thermal performance, heat transport capacity, and operational limits of the heat pipe. The aim of the experiment is to assess the heat pipe's performance under different operating conditions, such as varying heat loads. The study aimed to understand the heat transfer limitations and advantages of water-based heat pipes, which can have practical implications for numerous applications, such as electronics cooling, solar thermal systems, and space technology

Utilizing Ragone framework for optimized phase change material-based heat sink design in electronic cooling applications

This study explores the latent thermal energy storage potential of an organic phase change material with porous copper foam and its applicability in electronic cooling under varying heat load conditions. The organic phase change material, n-eicosane, is known for its inherently low thermal conductivity of 0.15 W/mK, rendering it vulnerable during power spikes despite its abundant latent heat energy for phase transition from solid to liquid. Porous copper foams are often integrated into n-eicosane to enhance the composite's thermal conductivity. However, the volume fraction of the phase change material in the porous foam that optimally improves the thermal performance can be dependent on the boundary condition, the cut-off temperature, and the thickness. A finite difference numerical model was developed and utilized to ascertain the energy consumption for the composite of n-eicosane with two kinds of porous copper foam with varying porosity under different heat rates, cut-off temperatures, and thickness. In addition, the results are compared with a metallic phase change material (gallium), a material chosen with a similar melting point but significantly high thermal conductivity and volumetric latent heat. For validation of the numerical model and to experimentally verify the effect of boundary condition (heat rate), experimental investigation was performed for n-eicosane and high porosity copper foam composite at varying heat rates to observe its melting and solidification behaviors during continuous operation until a cut-off temperature of 70 °C is reached. Experiments reveal that heat rate influences the amount of latent energy storage capability until a cutoff temperature is reached. For broad comparison, the numerical model was used to obtain the accessed energy and power density and generate thermal Ragone plots to compare and characterize pure gallium and n-eicosane - porous foam composite with varying volume fractions, cutoff temperature, and thickness under volumetric and gravimetric constraints. Overall, the proposed framework in the form of thermal Ragone plots effectively delineates the optimal points for various combinations of heat rate, cut-off point, and aspect ratio, affirming its utility for comprehensive design guidelines for PCM-based composites for electronic cooling applications

Control of Carbon Dioxide Bivalent Heat Pump on Heating of Buildings

The scheme of a bivalent heat pump (BHP) is considered, using both the heat of the water from the return network and the heat of the outside air as low-potential heat sources (LPH). The aim of the work is to create a BHP circuit that provides functioning at the variable heat load temperature. The goal was achieved by solving the following problems: analysis of methods of synthesis of BHP circuits, analysis of circuit operation under random disturbances and development of the automatic control systems for BHP. The most significant result of the work is: a heat pump circuit that can operate at variable pressures of the evaporator and the gas cooler. The next significant result is, for bivalent heat pumps intended for operation in heat supply systems with qualitative and qualitative-quantitative laws of thermal control, the introduction into the heat pump circuit of a heat exchanger installed in the return water circuit of the secondary building and cooled by outside air, as well as two control valves installed in series between the gas cooler and the evaporator, the first valve installed along the refrigerant flow being controlled by a signal based on the pressure difference between the outlet of the gas cooler and the separation vessel between the evaporator and the gas cooler, and the second by pressure in front of the evaporator. The significance of the obtained results lies in the increase of the COP of the heat pump, due to the increase of heat transfer in the gas cooler circuit. The HHP circuit differs from the known ones in that it uses two control valves and the heat exchanger for additional cooling of the return water of the BHP heated building.

Transient behavior of flow boiling in structured microchannels under sudden and highly variable heat loads

In practice, heat sinks are sometimes exposed to sudden and irregular or highly variable heat loads. Therefore, here, for expanding micro-pin-fin heat sinks having micro cavities (heat sink code: MD) transient flow boiling characteristics are investigated under sudden and highly variable heat loads. Results are compared with those of conventional parallel channel heat sink (SD). Experiments can be grouped into two categories: (1) For a specified mass flux (G = 200 kg m−2 s−1) and inlet temperature (Ti = 78 °C), different heat loads (150 W, 30 W, 200 W, 150 W and 30 W, respectively) are applied. Every heat load is applied for three minutes, successively. (2) For a given mass flux (G = 200 kg m−2 s−1) and different inlet temperatures (Ti = 36 °C, Ti = 57 °C and Ti = 78 °C), the heat sinks are suddenly exposed to heating power of 200 W for ten minutes. It is deduced that MD increases heat transfer coefficient, decreases pressure drop and enhances thermal response characteristics compared to SD. In whole experimental range, heat transfer coefficient increases up to 11,802%, decrease in surface temperature reaches up to 39.2 °C, decrease in pressure drop reaches up to 4.05 kPa, and time passed for stable thermal conditions reduces from 48 s to 25 s. Decreasing inlet temperature increases thermal performance, however, leads higher fluctuations.

Real-time optimization of the liquid-cooled data center based on cold plates under different ambient temperatures and thermal loads

With the advent of the information age, the scale of data centers has developed unprecedentedly, in which the cooling system consumes a lot of energy. Therefore, it is crucial to adjust the operating parameters in real-time to maximize energy savings. In this article, the mathematical models of each component are established, and the functions of system power consumption and chip temperatures are obtained for the liquid-cooled data center based on cold plates. The method proposed in this article has good accuracy through experimental verification and can be used for the optimization of operating parameters. The server chips in data centers need to be maintained within a safe range, so we take the minimum system power consumption as the optimization goal and the chip temperature as the constraint condition to calculate the optimal cooling tower wind volume, primary side flow rate, and secondary side flow rate under different environmental temperatures and heat loads, and fit all three for real-time optimization and regulation. The results show that the intelligent control proposed in this article can save 42.7% energy and reduce PUE to 1.16 under variable heat load, and save 30.6% energy and improve PUE by 4.3% under variable environmental temperature. The intelligent control method described in this article provides guidance for real-time optimization in data centers.

Experimental study on variation characteristics of combustion heat load in circulating fluidized bed under fuel high-temperature preheating modification

This study introduces an innovative application of fuel high-temperature preheating modification technology to circulating fluidized bed (CFB), intending to enhance the variable load rate of CFB and reduce its NOx emissions. The variable combustion heat load (CHL) experiments were conducted on a novel CFB experimental platform comprising a preheating modification device (PMD) and CFB. The findings indicate that implementing fuel high-temperature preheating modification technology allows the CFB to operate stably within the range of 30%–100% CHL while maintaining superior combustion efficiency. Moreover, it reduces NOx emissions by over 28% compared to conventional combustion. The decrease in NOx emissions can be attributed to the fuel's preheating modification process inhibiting NOx production and establishing conditions conducive to NOx reduction in CFB. Furthermore, after employing the fuel high-temperature preheating modification technology, the CHL change rate of CFB reached 1.79%/min and 2.27%/min for the transition from 50% CHL to 75% CHL and from 75% CHL to 100% CHL, respectively. These rates represent an increase of 1.59 and 1.80 times compared to the rates observed in conventional combustion processes. The increase in the CHL change rate of different CHL variation intervals is primarily due to the production of high-temperature coal gas and modified char following fuel preheating modification. High-temperature coal gas exhibits a rapid combustion rate, while modified char has a smaller particle size, more developed pore structure, and enhanced reactivity than raw coal.

Performance assessment of a geometrical modification on thermosyphon heat pipe with the assistance of novel convergent-divergent truncated cones for energy recovery systems

Heat pipe technology has evolved significantly in addressing thermal management challenges. Still, existing heat pipe designs have limitations in efficiently optimizing heat transfer, particularly in scenarios with spatial constraints and variable heat loads. To overcome these challenges, this study deals with incorporating truncated cones in different forms, such as convergent and divergent, in the thermosyphon heat pipe. The parametric analysis and the performance of this research highlight the ability to handle varying heat loads and determine that a 1:1:1 ratio between the evaporator, adiabatic, and condenser sections of 300 mm in total length thermosyphon heat pipe may be expected to meet spatial constraints efficiently. Placement of the convergent truncated cone in the evaporator and the divergent truncated cone in the condenser helps improve the evaporation and condensation performance by 62.07% and 108%, respectively, when compared to the conventional geometry due to the increasing vapour and liquid velocities. Interestingly, the wall temperature decreases by 11.9%, and the thermal resistance is reduced, increasing the heat transfer coefficient by 85.68% compared to the uniform geometry thermosyphon heat pipe. Hence, these findings provide a path for promising applications in heat recovery and thermal management systems.

Genetic analysis of phenotypic indicators for heat tolerance in crossbred dairy cattle

Climate change-induced rise in global temperatures has intensified heat stress on dairy cattle and is contributing to the generally observed low milk productivity. Selective breeding aimed at enhancing animals’ ability to withstand rising temperatures while maintaining optimal performance is crucial for ensuring future access to dairy products. However, phenotypic indicators of heat tolerance are yet to be effectively factored into the objectives of most selective breeding programs. This study investigated the response of milk production to changing heat load as an indication of heat tolerance and the influence of calving season on this response in multibreed dairy cattle performing in three agroecological zones Kenya. First-parity 7-day average milk yield (65 261 milk records) of 1 739 cows were analyzed. Based on routinely recorded weather data that were accessible online, the Temperature-Humidity Index (THI) was calculated and used as a measure of heat load. THI measurements used represented averages of the same 7-day periods corresponding to each 7-day average milk record. Random regression models, including reaction norm functions, were fitted to derive two resilience indicators: slope of the reaction norm (Slope) and its absolute value (Absolute), reflecting changes in milk yield in response to the varying heat loads (THI 50 and THI 80). The genetic parameters of these indicators were estimated, and their associations with average test-day milk yield were examined. There were no substantial differences in the pattern of milk yield response to heat load between cows calving in dry and wet seasons. Animals with ≤50% Bos taurus genes were the most thermotolerant at extremely high heat load levels. Animals performing in semi-arid environments exhibited the highest heat tolerance capacity. Heritability estimates for these indicators ranged from 0.06 to 0.33 and were mostly significantly different from zero (P < 0.05). Slope at THI 80 had high (0.64–0.71) negative correlations with average daily milk yield, revealing that high-producing cows are more vulnerable to heat stress and vice versa. A high (0.63–0.74) positive correlation was observed between Absolute and average milk yield at THI 80. This implied that low milk-producing cows have a more stable milk production under heat-stress conditions and vice versa. The study demonstrated that the slope of the reaction norms and its absolute value can effectively measure the resilience of crossbred dairy cattle to varying heat load conditions. The implications of these findings are valuable in improving the heat tolerance of livestock species through genetic selection.

Characterization of a Rack-Level Thermosyphon-Based Cooling System

Abstract This study aims to improve the combined energy efficiency of data center cooling systems and heating/cooling systems in surrounding premises by implementing a modular cooling approach on a 42 U IT rack. The cooling solution uses a close-coupled technique where the servers are air-cooled, and the air in turn is cooled within the rack enclosure using an air-to-refrigerant heat exchanger. The refrigerant passively circulates in a loop as a thermosyphon, making the system self-sustaining during startup and shutdown, self-regulating under varying heat loads, and virtually maintenance-free by eliminating mechanical parts (other than the cabinet fans). A heat load range of 2 kW–7.5 kW is tested on a prototype system. Experimental results reveal stable thermosyphon operation using R1233zd(E) as the working fluid, a maximum evaporator pressure drop of 21.5 kPa at the highest heat load and a minimum thermosyphon resistance of 6.8 mK/W at a heat load of 5.7 kW. The air temperature profile across the load banks (server simulators) and evaporator follow the same profiles with varying heat loads. Heat losses from the cabinet due to natural convection and radiation are of the order of several Watts for heat loads below 4 kW and rise sharply to 1 kW at the highest heat load tested. The system time constant is determined to be 25 min. The heat recovery process can be financially and environmentally beneficial depending on the downstream application.

Experimental study on a rectangular evaporator loop heat pipe with a phase-change material heat sink

To satisfy the heat dissipation requirements of high heat flux electronic devices in extreme conditions where no suitable heat sink exists, such as in the flight process of hypersonic aircraft and the re-entry process of spacecraft, a rectangular evaporator loop heat pipe (LHP) with a phase-change material heat sink was designed and developed. Extensive experimental studies on the thermal control performance of the LHP have been performed, mainly including the startup performance, maximum temperature control time, dynamic response to varying heat load, and the heat transfer limit. Experimental results showed that the LHP could successfully realize the startup at a small heat load as low as 5 W. Under 100 W heat load, the LHP can keep operating for 4 h and 16 min at most with the operating temperature lower than 50 °C, including 2 h and 40 min of quasi-stable operation. The heat transfer limit of the LHP could reach up to 200 W, corresponding to a heat flux of 13.3 W/cm2 at the evaporator. In addition, the LHP exhibited excellent dynamic response characteristics to varying heat loads, holding great application potential in future thermal control tasks in extreme conditions.

Modelling and simulation of heat flow in indexable insert drilling

In machining, the heat generated during the process deforms the components and the final shape might not meet specified tolerances. There is therefore a need for a compensation strategy which requires knowledge of the workpiece temperature field and the associated thermal distortions. In this work, a methodology is presented for the determination of the heat load for indexable insert drilling of AISI 4140. Compared to previous research, this work has introduced a varying heat load. The heat load is extracted from thermo-mechanical finite element simulations for different nominal chip thicknesses and cutting speeds using the coupled Eulerian-Lagrangian formulation of an orthogonal turning process. The heat load is then transferred to a simplified 2D axisymmetric heat transfer model where the in-process temperature field in the workpiece is predicted. To verify the methodology, the predicted temperatures are compared to the experimentally measured temperatures for various feed rates. It is found that the model is capable of predicting the workpiece temperatures reasonably well. However, the methodology needs to be further explored to validate its applicability.

Energy saving during the partial heat load period by integrating a steam-heated absorption heat pump into the thermal scheme of a PT-60/70-130/13 steam turbine

&#x0D; &#x0D; &#x0D; The task of determining the efficiency of operation of an absorption heat pump (AHP) with steam heating (COP conversion factor = 1.71) integrated into the thermal circuit of a PT-60/70-130/13 steam turbine that releases production steam and hot water during the partial heat load period (spring and autumn; also referred to as the inteheating period) is being solved in this paper. Variants of operation of the PT-60/70-130/13 with an integrated AHP with a capacity of ~17.25 MW in the partial heat load period were studied when steam with parameters of 1.296 MPa, 280°C was realised in the production selection of the adjustable turbine at flow rates of 20, 30, and 50 t/h with a variable heat load on hot water supply, which was determined by the return network water consumption task 1000–1400 t/h, while the ‘useful’ electrical power of the power complex was provided at ~30 MW. At electricity prices of 0.13 USD/(kWh) and standard fuel of 309 USD/t for Ukraine, the simple payback period of 17.25 MW AHP as part of the PT-60/70-130/13 steam turbine for the partial heat load period at a production load of 20–50 t/h of steam at the consumption of return network water of heat supply 1000–1200 t/h can decrease to two years. At the same time, during the partial heat load period, which lasts ~4404 hours in Ukraine, up to ~1.2% of fuel, up to 44% of technical water for feeding the circulation cooling system, and 0.4% of softened water for feeding are saved. A tangible environmental effect is achieved due to the reduction of harmful emissions – actual heat and hazardous gases – to the atmosphere: CO2 by 1118.7 tons, NOx by 5.87 t, thus saving ~41,000 of technical water.&#x0D; &#x0D; &#x0D;

Numerical investigation on non-linear streaming effects in a two-stage coaxial pulse tube cryocooler

Stirling pulse tube cryocoolers (PTC) are widely used in aerospace applications for the cooling of infrared sensors and for filtering background thermal noise in the astro-imaging devices, etc. Present investigation aims to use numerical methods to demonstrate the nonlinear fluid flow, heat transfer, and vortex generation phenomena in a two-stage coaxial type inertance pulse tube cryocooler. The numerical simulation is conducted using commercially available Fluent® code for both single-stage and multi-stage configurations to show nonlinear processes with varying heat load conditions. It has been noticed that the width of the vortex produced inside the pulse tube grows with an increase in heat load capacity. This undesirable flow conditions yields an adverse effect in the cooling behavior and reduces overall performance of cryocooler with higher heat load. Additionally, streamlines, stream function, pressure and temperature variation plots are given for both stages with different heat load capacity to substantiate our results.