Cooling Water Temperature Research Articles

Experimental study of direct contact condensation of spent vapor in a cocurrent flow packed tower under negative pressure

AbstractCondensers are often required in power generation systems to condense the exhaust steam generated at the end of the turbine. This paper will investigate the enhanced condensation process of spent steam in a parallel flow type. The operating parameters of steam temperature (Tcond), steam flow rate (Gin), cooling water temperature (Tin), and cooling water flow rate (Lw) will affect the condensation effect by changing the gas–liquid arrangement in the tower. In this experiment, an orthogonal test was designed in the Raschig ring to investigate the significance of these four operating parameters on the experimental results. Different types of packings have different condensation effects due to different accumulation methods. The same type of packing has a different surface area, resulting in different contact areas between the gas and liquid phases during condensation. In this experiment, four different packings will be investigated to find their condensation performance. This paper uses the size of subcooling (ΔT) as an indicator to evaluate the effectiveness of condensation, and the values of condensation rate (R), number of liquid phase heat transfer units (NTUL), and total volume heat transfer coefficient (Kv) are used as a reference for the effectiveness of condensation. The results show that the overall condensation effect of regular packing is better than that of random packing, The average condensation rate of regular packing is 95%, the average condensation rate of random packing is 90%, the subcooling of regular packing is about three to five smaller than that of random packing, the heat transfer coefficient of regular packing is about 1.5 times of that of random packing. And by fitting the Kv data for different packings, an empirical formula was obtained that can be used to predict the Kv size of other packings.

Exergy analysis of a negative CO[formula omitted] emission gas power plant based on water oxy-combustion of syngas from sewage sludge gasification and CCS

A power cycle with water-injected oxy-combustion (water cycle) is investigated by exergy analysis. It is fueled with syngas (aka. producer gas) from gasification of sewage sludge. The cycle is equipped with a spray-ejector condenser (SEC). CO2 is separated and compressed for transportation and storage. The net delivered electric power is 31% of the fuel exergy. The task efficiency is 39% when the flue gas bleed to gasification and O2 penalty are subtracted from fuel, and CO2 capture is included in the useful product. The large part of exergy destruction, 80%, pertains to the combustor. Increasing the temperature or the pressure of the combustor outlet (turbine inlet) lead, as expected, to reduced exergy destruction and more power delivery. Reducing pressure of the gas turbine outlet (SEC inlet) also increases power production. Varying pressure and temperature of the SEC outlet affects the distribution of exergy destruction among units of the condenser, however scarcely the overall efficiency. Reducing the ambient temperature, including cooling water temperature, reduces the efficiency of the plant, contrary to the effect of conventional plants. The reason is that the low pressure of SEC relies on the pressure and mass flow of injected water, rather than the temperature.

An effective PEMFC system shutdown purge strategy for improving the purging effect of liquid water and the dehydration of stack

The shutdown process is one of the critical stages when the proton exchange membrane fuel cell system runs as an actual application. Finding the effect of system operating conditions on shutdown purging could improve the purging effect of liquid water and the dehydration of the stack. In this study, an automotive fuel cell system of 350 single cells was developed on the vehicle scale and tested for factors that influence shutdown process. Seven shutdown purge cases for about 150 s were studied to investigate the shutdown purge strategy. It was found that 100% bypass valve opening reduced the purge time and improved the purge efficiency. The HCP speed should not be too slow or too fast in the shutdown process. The higher temperature of coolant water favored rapid shutdown and purge, and a large stoichiometric ratio of the cathode inlet improved the purge effect but enhanced the energy consumption of the air compressor. Neither too high nor too low purge pressure could blow out the liquid water more efficiently and improve the ohmic resistance. During purging, current density mainly influenced the water production rate and the maintenance state of stack temperature. With a higher stack temperature, purge process with a small current density could quickly reduce the stack humidity and enhance the ohmic resistance. Accelerating the opening rate of the anode purge valve could not effectively accelerate purge effect of the stack, while extending the valve closing time could improve hydrogen utilization. Future studies to investigate the combined impact of these factors on the fuel cell system shutdown purge will be carried out to develop the most effective strategy.

The effect Cooling Water Temperature in Air Gap Membrane Distillation for Breaking of Butyric acid – Water Azeotrope

The effect Cooling Water Temperature in Air Gap Membrane Distillation for Breaking of Butyric acid – Water Azeotrope

Modern approaches ensuring rational conditions for continuously cast billet formation in a billet CCM mold.

The development of technology and technology of continuous steel casting actualizes the improvement of the control system of casting processes and diagnostics of the formation of continuously cast billets. The conditions determining the stability of continuous cast billet forming process in billet CCM mold are considered: the correspondence of liquid steel mass entering the mold and the outgoing billet mass; ensuring the specified intensity and uniformity of billet cooling in the mold sleeve; ensuring a rational level of friction in the crystallizer. It is shown that, on the one hand, heat transfer in the mold is largely determined by the correspondence of the billet shrinkage and the internal profile of the mold, but, on the other hand, it is noted that it is impossible to obtain a universal profile that creates optimal conditions for the formation of billets from all grades of steel with arbitrary temperature-speed parameters. Therefore, the concept of a universal crystallizer assumes that rational conditions of heat removal are achieved due to additional influences. The basics of diagnosing of heat exchange processes in the crystallizer are presented, based on the computational processing of the current ACS signals about the cooling water temperature drop in the crystallizer and its flow rate. It is noted that this system, unfortunately, does not guarantee the detection of local unevenness of the heat removal in the crystallizer and needs to be improved by providing the possibility of assessing the billet faces cooling uniformity. Modern approaches to optimize internal profile of crystallizer sleeves, choice of materials for coating inner surface of sleeves, choice of parameters of mold swinging system and diagnostics of parameters of force interaction between crust of forming billet and mold sleeve are briefly considered on issue of friction rational level establishing. The creation of a “universal” crystallizer with an increased number of control systems and the creation of a system for optimization of casting processes for specific conditions are identified as possible directions for the development of approaches to ensure rational conditions for the formation of continuous cast billets in the crystallizer of a billet caster.

TransFNN: A Novel Overtemperature Prediction Method for HVDC Converter Valves Based on an Improved Transformer and the F-NN Algorithm.

Appropriate cooling of the converter valve in a high-voltage direct current (HVDC) transmission system is highly significant for the safety, stability, and economical operation of a power grid. The proper adjustment of cooling measures is based on the accurate perception of the valve's future overtemperature state, which is characterized by the valve's cooling water temperature. However, very few previous studies have focused on this need, and the existing Transformer model, which excels in time-series predictions, cannot be directly applied to forecast the valve overtemperature state. In this study, we modified the Transformer and present a hybrid Transformer-FCM-NN (TransFNN) model to predict the future overtemperature state of the converter valve. The TransFNN model decouples the forecast process into two stages: (i) The modified Transformer is used to obtain the future values of the independent parameters; (ii) the relation between the valve cooling water temperature and the six independent operating parameters is fit, and the output of the Transformer is used to calculate the future values of the cooling water temperature. The results of the quantitative experiments showed that the proposed TransFNN model outperformed other models with which it was compared; with TransFNN being applied to predict the overtemperature state of the converter valves, the forecast accuracy was 91.81%, which was improved by 6.85% compared with that of the original Transformer model. Our work provides a novel approach to predicting the valve overtemperature state and acts as a data-driven tool for operation and maintenance personnel to use to adjust valve cooling measures punctually, effectively, and economically.

Investigation of condensate droplet movement in marangoni condensation of ethanol-water mixtures by infrared thermography

Marangoni condensation is a phenomenon that occurs during the condensation of a positive system with binary vapor mixtures. Applying infrared thermography to the investigation of Marangoni condensation could not only help to obtain quantitative data on droplet movement but also establish the relationship between the droplet velocity and surface temperature of condensate droplets. In this study, the droplet movement in Marangoni condensation of ethanol-water mixtures was experimentally investigated by infrared thermography. The effects of vapor concentration, impinging cooling water temperature, and vapor velocity on droplet velocity were investigated, and the relationships between droplet velocity, temperature gradient, and surface tension gradient were studied. The results indicated that the droplet velocity first increased and then decreased with the increase in the droplet radius. The maximum droplet velocity decreased with the increase in vapor concentration and vapor velocity. As impinging cooling water temperature increased, the droplet velocity decreased, and the decline was more obvious at the high impinging cooling water temperature. In addition, the droplet velocity increased and then decreased with the increase in the surface temperature gradient and surface tension gradient.

Numerical study of particle deposition characteristics in a new type of reinforced pipe

When the heat exchanger is working, the medium often contains small impurity particles. Some particles will form dirt in the tubeline during operation, thus increasing energy consumption. This paper presents a new type of reinforced heat exchange tube. The Lagrange model and User-defined Function (UDF) in FLUENT software are used to compile the particle deposition judgment conditions, establish the particle ablation model, and study the effects of inlet flow rate, inlet temperature and particle size on the particle deposition characteristics of straight, twisted and new tubes. The liquid results showed that when the inlet flow rate is 0.6 m/s, the inlet cooling water temperature is 27 °C, the outer wall temperature is 78 °C, the wall roughness is 0.05 mm, and the particle size is 1 μm. When the particle mass flow rate is 0.0005 kg/s, the particle deposition rate in the new tube reaches the minimum value of 30.1% at 19.2 h These data showed that the structure of the new tubeline will not only cause the fluid to rotate, but also cause the fluid to expand and contract, thus increasing the turbulence. The new enhanced heat exchange tube has excellent performance in inhibiting particle deposition.

Numerical and experimental investigation of a novel liquid upper-feeding micro-channel flat loop thermosyphon cooling and heat recovery system

ABSTRACT A novel liquid upper-feeding micro-channel flat loop thermosyphon (LUF-MCFLTS) system was developed, to eliminate the drying phenomenon of the upper surface in the traditional LTS and provide a highly efficient solution for DC cooling and heat recovery. The effects of cooling capacity (cooling water flow rate and temperature), heat load, and filling ratio on the heat transfer performance of the LUF-MCFLTS system are investigated experimentally. The results indicated that with the increase in cooling water flow, the decrease in cooling water temperature, and the increase in heat load, the heat transfer performance of the LUF-MCFLTS system was better. Under a heat load of 500 W, a cooling water flow rate of 600 L/h, and a cooling water temperature of 15°C, the heat recovery efficiency could reach 86.28%. Compared with the MCFTS and MCFLTS systems in literature, the recovery efficiency of the LUF-MCFLTS system could be increased by 31.6% and 2.64%, respectively. In addition, an effective numerical model to predict the heat recovery efficiency of the LUF-MCFLTS system with the experimental data in the 2.07% error band has been established. This work provides a new idea and theoretical basis for the design of DC cooling and heat recovery system.

Experimental investigations of liquid immersion cooling for 18650 lithium-ion battery pack under fast charging conditions

In this study, a novel battery thermal management system (BTMS) based on FS49 is proposed and tested for cooling the cylindrical lithium-ion battery (LIB) module under fast charging conditions. Firstly, the temperature response of the battery module under 2 C and 3 C rates charging with forced air cooling (FAC) and liquid immersion cooling (LIC) is compared. The results indicate that the LIC has excellent heat dissipation performance, and the peak temperature of the module during 2 C and 3 C rates charging are reduced by 7.7 °C and 19.6 °C, respectively, compared with the FAC, while the corresponding cooling energy consumption of LIC is only 14.41% and 40.37% of the FAC. Meanwhile, the LIC embraces the advantages of minimizing the temperature non-uniformity in battery pack. The corresponding peak temperature difference of the module is just 1.1 °C and 1.2 °C, which is only 17.7% and 11.6% of that under FAC. Subsequently, the thermal management performance of the proposed LIC is investigated under conventional C rate discharging and different fast charging schemes. Finally, effect of condenser flow rate and cooling water temperature were investigated. This study demonstrates the application prospect of the LIC in the field of LIB fast charging.

Industrial experiment and numerical analysis of the effect of pulsing water flow in thermoelectric generators

Thermoelectric conversion technology can effectively recover industrial waste heat and improve industrial energy utilization efficiency. Most of the industrial waste heat is released irregularly, making it difficult for the thermoelectric generator (TEG) to achieve optimal power generation performance. In order to improve the power generation performance of the TEG in the industrial environment, it is a simple and efficient method to control the internal temperature gradient of the TEG by pulsing water flow. In this study, the numerical calculation method is used to analyze the effect of cooling water conditions on the performance of the TEG in an industrial environment. The numerical calculation process is divided into two parts: steady calculation and transient calculation. Steady calculations are used to analyze the effect of cooling water's initial temperature and flow rate. The cooling water reduces the temperature of the hot end of the thermoelectric module (TEM), which prevents the TEM from reaching the maximum temperature gradient. The flow condition of cooling water is changed to pulse flow, which is used to adjust the temperature gradient of the TEM. The transient calculation is used to analyze the effect of different pulse conditions in TEG's performance. According to the numerical calculation results, industrial experiments are designed, and the experimental results verify the accuracy of the numerical calculation results. The results show that when the cooling water temperature is 20 °C and the flow rate is 3 ms−1, the power generation performance of the TEG reaches the best state. The maximum output power is 281.2 W. Pulsing water flow improves TEG power generation performance. The output power of the TEG is increased by 8.43% when the pulse condition is 0.3 s, and the output power is 304.64 W.

Numerical simulation of CO2 two-stage compression refrigeration system with external intercooler

The CO2 two-stage compression refrigeration system is a feasible alternative to conventional refrigeration systems for logistics cold storage cooling that provides high efficiency and environmental protection. In a previous study, we proposed a two-stage compression refrigeration cycle with an external intercooler and performed a thermodynamic analysis. Based on that, a more comprehensive simulation analysis is performed herein using the validated models. The performance, optimal discharge pressure, and intermediate pressure are investigated using a high-pressure compressor with both fixed and variable speeds. The results show that the cooling-water temperature has a significant positive linear correlation with the optimal discharge pressure, whereas the evaporator-inlet air temperature has little effect at a fixed high- pressure compressor speed. When the high-pressure speed is adjusted to achieve the optimal intermediate pressure and discharge pressure simultaneously, the coefficient of performance increases by 4.5% compared with that of the fixed-speed system, while the cooling capacity decreases by 8.4%. The correlation of optimal discharge pressure and optimal intermediate pressure is given.

Model-based decoupling control for the thermal management system of proton exchange membrane fuel cells

As one of the most promising sustainable energy technologies available today, proton exchange membrane fuel cell (PEMFC) engines are becoming more and more popular in various applications, especially in transportation vehicles. However, the complexity and the severity of the vehicle operating conditions present challenges to control the temperature distribution in single cells and stack, which is an important factor influencing the performance and durability of PEMFC engines. It has been found that regulating the input and output coolant water temperature can improve the temperature distribution. Therefore, the control objective in this paper is regulating the input and output temperature of coolant water at the same time. Firstly, a coupled model of the thermal management system is established based on the physical structure of PEMFC engines. Then, in order to realize the simultaneous control of the inlet and outlet cooling water temperature of the PEMFC stack, a decoupling controller is proposed and its closed-loop stability is proved. Finally, based on the actual PEMFC engine platform, the effectiveness, accuracy and reliability of the proposed decoupling controller are tested. The experimental results show that with the proposed decoupling controller, the inlet and outlet temperatures of the PEMFC stack cooling water can be accurately controlled on-line. The temperature error range is less than 0.2 °C even under the dynamic current load conditions.

Assessment of the two-phase thermosyphon loop with high filling ratio under anti-gravity

In various fields of thermal management and protection, such as vehicles, aircraft, and mobile electronic devices, it is crucial to transfer heat effectively from the top to the bottom. The use of a simple structure for this transfer can reduce the weight of the heat transfer system. Theoretical studies have demonstrated that the two-phase thermosyphon loop (TPTL) with a high filling ratio has the potential for excellent performance in anti-gravity applications. In this study, we investigate the thermal performance of a high filling ratio TPTL under anti-gravity conditions. Our results reveal that, contrary to previous understanding, a TPTL with a high filling ratio can effectively transfer heat in anti-gravity. However, we also found that the loop thermal resistance of TPTL under anti-gravity is greater than under gravity, and the heating surface temperature is higher. Additionally, we experimentally study the effect of inclination angles on anti-gravity performance, and our results indicate that smaller angles result in better heat transfer. Finally, we investigate the impact of cooling water temperature on thermal performance. Overall, considering the energy efficiency of the heat dissipation system and the heat transfer capacity of the device, it is not recommended to use cooling water at a lower temperature. This research sheds light on the potential for TPTLs to operate in anti-gravity conditions and supports their practical applications.

Experimental study and information entropy analysis on periodic performance of a PCM thermal management system for blade servers in data centers

The high power of blade servers inside small data centers (DCs) can cause heat accumulation, which can degrade the performance of DCs. To address the problem of heat dissipation, we performed periodic experiments on a thermal management system based on a phase change material. The effects of time ratio, heating power, and cooling water temperature on the performance of thermal control and periodic stability were investigated. Information entropy reflects uncertainty by transforming a variable changes over time into a single parameter representing inhomogeneity of time. Herein, it was introduced as an evaluation index of thermal control performance. The results verified that the peak temperature of the heating surface can be maintained below 80 °C for several periods under specific conditions. Additionally, the information entropy results of the experimental data reflected the thermal control performance of the system and validated the experimental conditions. Based on the experimental results and the corresponding information entropy analysis, we proposed a design strategy for the system parameters and a method for reducing the number of measuring points. The obtained results formed the basis for the thermal management design of the server level of DCs, other electronic equipment, and electric vehicles.

A New Conformal Penetrating Heating Strategy for Atherosclerotic Plaque

(1) Background: A combination of radiofrequency (RF) volumetric heating and convection cooling has been proposed to realize plaque ablation while protecting the endothelial layer. However, the depth of the plaque and the thickness of the endothelial layer vary in different atherosclerotic lesions. Current techniques cannot be used to achieve penetrating heating for atherosclerosis with two targets (the specified protection depth and the ablation depth). (2) Methods: A tissue-mimicking phantom heating experiment simulating atherosclerotic plaque ablation was conducted to investigate the effects of the control parameters, the target temperature (Ttarget), the cooling water temperature (Tf), and the cooling water velocity (Vf). To further quantitatively analyze and evaluate the ablation depth and the protection depth of the control parameters, a three-dimensional model was established. In addition, a conformal penetrating heating strategy was proposed based on the numerical results. (3) Results: It was found that Ttarget and Tf were factors that regulated the ablation results, and the temperatures of the plaques varied linearly with Ttarget or Tf. The simulation results showed that the ablation depth increased with the Ttarget while the protection depth decreased correspondently. This relationship reversed with the Tf. When the two parameters Ttarget and Tfwere controlled together, the ablation depth was 0.47 mm-1.43 mm and the protection depth was 0 mm-0.26 mm within 2 min of heating. (4) Conclusions: With the proposed control algorithm, the requirements of both the ablation depth and the endothelium protection depth can be met for most plaques through the simultaneous control of Ttarget and Tf.

Optimum selection of temperature control measures for combined intake tower in alpine region during construction period

Due to the characteristics of complex climate, large temperature difference between day and night, and long winter in alpine region, concrete is prone to temperature cracks during the pouring process of intake tower. Therefore, it is crucial to adopt appropriate temperature control measures for concrete crack prevention of intake tower concrete in view of the local special climate. In this paper, a join intake tower in alpine region were taken as the project case. Additionally, the three-dimensional finite element simulation software is used to analyze the sensitivity of cooling water pipe spacing, cooling water supply time, cooling water temperature, insulation layer thickness, and thickness of pouring layer in foundation restraint zone, and the most favorable temperature control measure is selected based on the simulation results. In the optimum scheme, cooling pipe spacing is 1.5 m × 1.5 m, cooling water supply time is 15 d, cooling water temperature is 12Co, the insulation material is 10 cm foam sheet, and the thickness of pouring layer in foundation restraint zone is 1.5 m. When the optimum scheme is verified, the temperature and thermal stress of the intake tower meet the control standards. The research results can provide references for the design and construction of the joint intake tower project in Qinghai.

Spatial ecology of translocated American Eel (Anguilla rostrata) in a large freshwater lake

American Eel (Anguilla rostrata) undertake extensive migrations from their rearing grounds to spawn in the Sargasso Sea, and historically the upper St. Lawrence River and Lake Ontario provided an important source for large, fecund female eel. Following declines in the Lake Ontario population, glass eel were translocated from eastern Canada from 2006 to 2010. From 2016 to 2018, large, presumably translocated yellow eel (N = 230) with the potential to begin maturing and out-migrating within their year of capture were collected in spring and fall and tagged with acoustic transmitters. Eel were released into eastern Lake Ontario and tracked to better understand their movement patterns prior to and during migration, and the timing of migration. Most eels successfully migrated out of Lake Ontario (64%). Timing of migration was consistent regardless of year or tagging season and primarily occurred in late summer or fall, with cooling water temperatures and decreasing sky illumination associated with initiation for fall tagged eel. Eels were mostly detected in eastern Lake Ontario and those in western Lake Ontario were mostly detected in shallow waters (< 20 m) close to shore. Eels were detected on fewer receivers in the winter, suggesting reduced movements during this season. Finally, larger individuals spent less time in the system, particularly when tagged in the fall. These findings confirm that translocated eels can migrate out of Lake Ontario; however, the weeks when migration occurred were more aligned with timing in their natal range (i.e., eastern Canada) than with naturally recruited eels from Lake Ontario. This temporal mismatch requires further consideration, since it may influence arrival times of translocated eel to the spawning grounds and their recruitment potential. These results can be used to inform future assessments of eel translocation efficacy and can also aid in the design of future tracking studies to more completely explore the downstream migration success of eel translocated into the highly productive waters of Lake Ontario.

Higher conversion efficiency for combined systems with triple-junction GaAs photovoltaic cell and thermoelectric device

Photovoltaic (PV) and thermoelectric (TE) hybrid systems have the potential to increase solar energy utilization and possess broad development prospects. However, it is critical to select a suitable PV cell to couple with TE device and improve the efficiency of the photovoltaic–thermoelectric (PV-TE) hybrid system. This study used thermal interface materials (TIMs) with different thermal conductivities in triple-junction InGaP/GaAs/GeInG (tj-GaAs) PV-TE hybrid systems to reduce thermal contact resistance (TCR). The performance was investigated using a solar simulator with adjustable irradiation intensity and a liquid cooling device with controllable temperature. A comparative study has also been conducted with mono-crystalline (mc-Si) PV-TE system of the similar structure. The results indicated that the total output power of the direct contact PV-TE hybrid device and the optimized hybrid device using a thermal grease with a conductivity of 5.8 W m−1 K−1 could increase by 5.50% and 16.24%, respectively, compared with that of the pure PV. Moreover, lower cooling water temperatures have improved the performance of both PV cell and TE device. Results also indicated that the output power produced by the PV cell and TE device in the tj-GaAs PV-TE system are 537 mW and 0.76 mW higher than that produced by the PV cell and TE device in mc-Si silicon PV-TE system at 3.5 suns and 20 °C cooling water temperature, respectively. Compared to mc-Si PV cells, GaAs PV cells are more suitable for PV-TE hybrid systems and more adaptable under concentrated light conditions.

Study on heat transfer characteristics of flue gas condensation in narrow gap heat exchangers

Flue gas after wet desulfurization contains a large quantity of water vapor, as well as a small amount of fine particulate matter, acid and other pollutants. Direct emissions will cause haze and environmental pollution. Flue gas condenser can effectively recover latent heat of vaporization and remove these pollutants. However, the traditional flue gas condenser has disadvantages such as large volume, low heat exchange efficiency and easy blockage. To overcome these problems, a new type narrow gap heat exchanger, which is easy to detach and clean, is proposed. Then, the flue gas condensation characteristic is experimentally investigated. The factors including velocity and temperature of flue gas, flow and temperature of cooling water are studied on heat transfer coefficient and the condensation rate. The results indicate that the overall heat transfer coefficient is seven times of convection heat transfer coefficient, and the condensation rate can reach more than 60%. As the cooling water temperature increases, the condensation rate and condensation heat transfer coefficient gradually decrease. With the increasing of the flue gas velocity, condensation rate gradually decreases and condensation heat transfer coefficient gradually increases. Finally, the dimensionless correlation of Nusselt number is carried out, and the error is within 10%.