Cooling Water Temperature Research Articles

The vortex layer apparatus as a source of low-grade heat in the process of pretreatment of the substrate before anaerobic digestion

The limiting stage of anaerobic digestion (AD) of organic waste is the hydrolysis of particulate organic matter. One of the most promising and energy-efficient methods of waste pretreatment before AD is its processing in a vortex layer apparatus (VLA). The work was aimed at experimentally determining the energy characteristics of VLA. The description of the experimental plant and its energy balance were given. The ranges of electricity consumption and heat generation were shown. According to experimental data, the coefficient of conversion of electricity into heat was in the range of 0.367-0.515 at a cooling water temperature of 10.6-11.7 oC. Based on the experimental data obtained, it can be argued that VLA is a stable source of low-grade heat that can be utilized using heat pumps.

Simulation and parametric study on a novel modified Kalina cycle

To improve the utilization rate of hot dry rock resources, it is necessary to recover the energy of geothermal tailwater and improve the net output work. An improved ammonia-water power cycle is proposed based on the Kalina cycle. Taking the geothermal parameters of the Husavik Power Plant in Iceland as the prototype (the water temperature of the geothermal well is 122 °C, and the tailwater temperature is 80 °C), the numerical simulation of the modified Kalina cycle is carried out by using Engineering Equation Solver software. The result shows that the net power output of the modified Kalina cycle increases by 10.5% compared to that of the Kalina cycle. In addition, the parametric study shows that the optimal ammonia concentration of the basic solution in the general area is 0.9. The lower the cooling water temperature is, the lower the turbine exhaust pressure and the higher the net power output. When the ammonia concentrations of the basic solution are 0.6, 0.7, 0.8 and 0.9, the optimum pressures are 29 bar, 36 bar, 41 bar and 45 bar, respectively. The results of this study will contribute to the utilization of geothermal energy in hot dry rock.

Temperature distribution modeling of PV and cooling water PV/T collectors through thin and thick cooling cross-fined channel box

Many aspects relating to thermal, economic, and reliability challenges are involved while designing a Photovoltaic/Thermal (PV/T) system under high performance. When compared to standard PV systems, PV/T systems are more effective in locations with high irradiance. To eliminate the excess heat from a PVT system, an optimal cooling system is necessary, resulting in improved the temperature of PV module which directly effect on the overall performance. The current study is focused on a new economic and essay construction thin and thick (3 mm and 15 mm) cooling cross-fined channel box that have covered modeled. In terms of cell temperature and output cooling water temperature, the effects of various irradiation levels and cooling water flow rates are examined. Software that is based on finite elements, the problem was solved numerically in a three-dimensional model using ANSYS (19.2). It has been discovered that when the cooling fluid flow rate increases, the average surface temperature distribution of PV/T system and outlet cooling water temperature are reduced for thin and thick box heat exchanger and ideal with a cooling fluid flow rate of 3 L/min. The average surface temperature and water-cooling temperature are 30.7 °C and 38.9 °C for thin box heat exchanger, respectively, whereas for thick box heat exchanger are 30.8 °C and 32.4 °C, respectively, under solar irradiance 1000 W/m2 and optimal flow rate.

Thermal performance of hydrophobic α-Al2O3 ceramic membrane for solar-thermal membrane coupling water desalination process

A water desalination idea with high-efficiency was presented, which employed a vacuum tube type solar distiller to stuffy-thermal distillation and raw water preheating, and also utilized the hydrophobic α-Al2O3 ceramic membrane distillation (HCMD) modules and preheated raw water to membrane distillation (MD). In order to show the potential of HCMD to improve the photo-thermal conversion efficiency of the vacuum tube type solar distiller, this study explored the thermal performance and water desalination capacity of HCMD module driven by the recovered latent heat of the vacuum tube type solar distiller. The research results indicate that the membrane flux of HCMD had a significant positive exponential correlation with the raw water temperature (Tr). The convective heat transfer coefficient (h) of the hot side surface of hydrophobic α-Al2O3 ceramic membrane (HCM) was positively correlated with Tr and the concentration of raw water (C). The effects of Tr and cooling water temperature (Tc) on the thermal efficiency (η) of HCMD had an interaction. The theoretical maximum of η was close to 67.8%, and the variation range of η corresponding to the temperature range of preheated raw water by the solar distiller was 8.32–42.90%. The rejection rate of the HCM for all measured ions in the raw water was greater than 99.96%. This research was of great theoretical guiding significance for realizing the engineering application of the solar-thermal membrane coupling water desalination system.

Modeling and thermal management of proton exchange membrane fuel cell for fuel cell/battery hybrid automotive vehicle

The proton exchange membrane fuel cell (PEMFC) stack is a key component in the fuel cell/battery hybrid vehicle. Thermal management and optimized control of the PEMFC under real driving cycle remains a challenging issue. This paper presents a new hybrid vehicle model, including simulations of diver behavior, vehicle dynamic, vehicle control unit, energy control unit, PEMFC stack, cooling system, battery, DC/DC converter, and motor. The stack model had been validated against experimental results. The aim is to model and analyze the characteristics of the 30 kW PEMFC stack regulated by its cooling system under actual driving conditions. Under actual driving cycles (0–65 kW/h), 33%–50% of the total energy becomes stack heat; the heat dissipation requirements of the PEMFC stack are high and increase at high speed and acceleration. A PID control is proposed; the cooling water flow rate is adjusted; the control succeeded in stabilizing the stack temperature at 350 K at actual driving conditions. Constant and relative lower inlet cooling water temperature (340 K) improves the regulation ability of the PID control. The hybrid vehicle model can provide a theoretical basis for the thermal management of the PEMFC stack in complex vehicle driving conditions.

Simulation study of using macroporous ceramic membrane to recover waste heat and water from flue gas

Transport membrane condenser based on macroporous ceramic membranes can better meet the requirements of power plants for the recovery of waste heat and water from flue gas. This paper proposes a condensation and permeation model for describing the process of waste heat and water recovery from flue gas by macroporous transport membrane condenser. The results obtained from model are compared with the experimental results. According to results of condensation and permeation rate, errors between the calculated and experimental data are less than 10%. According to results of outlet water and flue gas temperatures, errors between the calculated and experimental results are within 0.06%. Therefore, accuracy of the model is verified. Based on the model, effects of the parameters including flue gas temperature and flow velocity, cooling water temperature and flow velocity, flue gas relative humidity, membrane porosity, and local atmospheric pressure are studied in terms of water and heat recovery performances. The research results show that increasing the flow rate of flue gas and cooling water, increasing the relative humidity of flue gas, increasing the local atmospheric pressure, reducing the temperature of flue gas and cooling water can increase the condensation rate of water vapor, thereby enhancing the recovery performance of the ceramic membrane. The increase of the porosity of the ceramic membrane can increase the penetration rate of the condensate, and more condensate can be recycled into the ceramic membrane, so that the overall recovery effect is better.

Experimental Analysis on Heat Release of Pulsating Heat Pipe Phase Change Regenerator with Different Working Fluids

In order to improve the problems of serious energy waste and low utilization rate, this paper designs and builds an experimental platform for a pulsating heat pipe type phase change heat storage device. The temperature changes with time in the heat storage and release device of the barium hydroxide octahydrate phase change material under different working conditions is studied. The results show that during the heat release process, when the pulsating heat pipe is filled with water, the cooling water temperature rises to the highest, and the heat recovery rate is as high as 64%. Otherwise, the initial temperature of the cooling water during the heat release process is studied. Result shows that the initial temperature of the cooling water increases, the longer the latent heat of phase change and the total heat release time, and the higher the temperature rise of the cooling water. The experimental design of this paper can provide a reference for researchers in related fields.

Experimental study on adsorption cooling performance of copper foams curing MIL-101/isobutane double bed system

In this paper, copper foams cured MIL-101(CFCM)/isobutane double-bed adsorption cooling system (ACS) were designed and constructed by using the CFCM unit tube adsorbers. Adsorption cooling characteristic curves of CFCM/isobutane double-bed ACS were studied. Influence of cycle parameters and mass recovery process on the cooling capacity, specific cooling power (SCP) and coefficient of performance (COP) of the CFCM/isobutane double-bed ACS was investigated. Results show that under the conditions of cycle time of 600 s, pre-cooling/pre-heating time of 120 s, condensation temperature of 15°C and hot water temperature of 85°C with the flow rate of 20 L h −1 , and cooling water temperature of 14-16°C with the flow rate of 50 L h −1 , the cooling capacity, SCP and COP of CFCM/isobutane double-bed ACS is 65.20 kJ kg −1 , 108.67 W kg −1 and 0.2260, respectively. Compared with basic cycle, the cooling capacity, SCP and COP of CFCM/isobutane double-bed ACS increases by about 26%, 24% and 22% under mass recovery time of 10 s. The cooling performance of CFCM/isobutane double-bed ACS remains stable after 100 sets consecutive basic cycles and 20 sets mass recovery cycles.

Transient performance study of an internally-cooled plate membrane liquid desiccant air dehumidification system

• An internally-cooled plate membrane liquid desiccant air dehumidification system has been applied. • A dynamic model for the novel dehumidification system is built up. • The transient performances of the system in a typical summer day are studied. • The temperatures of the solution in the solution tanks vary rapidly after starting up. • Increasing cooling water flow rate or reducing its temperature can improve the system performance. An internally-cooled plate membrane liquid desiccant air dehumidification system has been adopted for air dehumidification due to its excellent ability of removing moisture. In this study, a dynamic model for the novel system is built up by coupling the model of each component. Based on the experimental data and the steady-state model, the dynamic model is validated to prove its accuracy. The transient performances of the system in a typical summer day are investigated. It is found that the operation process of the system during the daytime includes the start-up period and the stable running period. Owing to the rapid change of system parameters, the performances of the system during the start-up period are studied in detail. The results show that the temperatures of the solution in the solution tanks vary rapidly after starting up because of the low thermal inertia. Increasing cooling water flow rate or reducing cooling water temperature can improve the SDP of the system. The initial solution concentration and the volume of solution in the tank have a great effect on the start-up time, while the initial solution temperature has little influences.

Thermoregulation of ocean sunfish in a warmer sea suggests their ability to prevent heat loss in deep, cold foraging grounds

During behavioural thermoregulation, it has been demonstrated that fish alter their heat exchange rates between warming and cooling. In the case of the ocean sunfish (Mola mola), there is a several-fold difference in the rate of heat exchange between foraging in the deep, cooler water and recovering body temperature at the warmer surface. Increased heat gain during warming has been suggested, but there is also the possibility of preventing heat loss during cooling. To examine this, we measured the vertical movement and muscle temperature of three captive sunfish that were released into the field under warmer conditions and compared them with previously reported sunfish that foraged in cooler deep water. The released sunfish vertically moved from near the surface, where the water temperature was 21–25 °C, to depths of 150–200 m, where the water temperature was 15–17 °C. All sunfish occasionally appeared on the sea surface and sometimes remained at the surface for <41 min. However, they reduced their muscle temperature by diving before their muscle temperature exceeded 21–22 °C, suggesting behavioural thermoregulation using the cooler water temperature at depth. In addition, the feeding events detected by video were limited to depths shallower than 60 m. This is in contrast from previously observed sunfish behaviour, in which fish were reported as recovering their body temperature using warmer temperatures at the surface after foraging in deep, cooler water. The heat-budget models indicated that the whole-body heat-transfer coefficients during warming in this study were similar to those of previously reported sunfish that had recovered their body temperature at the sea surface after foraging in deep, cooler water. In contrast, the heat-transfer coefficients at cooling in this study were higher than those of sunfish foraging in deep, cooler water. This suggests that ocean sunfish may have the ability to prevent heat loss in the physiological regulation of heat exchange rate during thermoregulation, while also indicating that sunfish have the ability to respond to changes in the temperature environment by altering their behaviour and heat exchange rate.

Research on Response Characteristics and Control Strategy of the Supercritical Carbon Dioxide Power Cycle

With the development of GEN-IV nuclear reactor technology, the supercritical carbon dioxide (SCO2) Brayton cycle has attracted wide attention for its simple structure and high efficiency. Correspondingly, a series of research has been carried out to study the characteristics of the cycle. The control flexibility of the power generation system has rarely been studied. This paper carried out a dynamic performance of the 20 MW-SCO2 recompression cycle based on the Simulink software. In the simulation, the response characteristics of the system main parameters under the disturbances of cooling water temperature, split ratio, main compressor inlet temperature and pressure were analyzed. The results show that the turbine inlet temperature is most affected by the disturbances, with a re-stabilization time of 2500–3000 s. According to the response characteristics of the system after being disturbed, this study proposed a stable operation control scheme. The scheme is coordinated with the main compressor inlet temperature and pressure control, recompressor outlet pressure control, turbine inlet temperature control and turbine load control. Finally, the control strategy is verified with the disturbance of reduced split ratio, and the results show that the control effect is good.

Experimental study of the potential for thermal energy recovery with thermoelectric devices in low displacement diesel engines

Improving the thermal efficiency of internal combustion engines is essential to reduce the operating costs and complaints with the increasing environmental requirements. Thermoelectric generators came up as an opportunity to reuse part of the heat loss with the exhausts. This paper evaluates the performance of a thermoelectric generator to improve the efficiency of a stationary diesel engine under different rotational speeds and torques. The data was obtained through CFD simulations and validated with experiments. The proposed solution uses a cooling system to control the temperature of the thermoelectric modules. The results show that the torque and the rotational speed of the engine are the most significant performance parameters of the thermoelectric generator, while the influence of the cooling water temperature has a minor but still significant influence. Additionally, the results show a change from 1.3% to 6.2% in the thermoelectric generator efficiency, while the exergy efficiency varies between 1.8% and 7.9%. The exergy balance indicates that most of the exergy is loss because of the irreversibilities in the thermoelectric generator and of the exergy loss with the exhausts. The exergy loss can be reduced by optimizing the design of the heat exchanger. Since the thermoelectric generator improved the engine efficiency by a marginal 0.2%–0.8%. Therefore, it is important to further research how to improve the design of heat exchangers for thermoelectric generators to increase their energy conversion efficiency and their impact on the energy efficiency of internal combustion engines.

Engineering design, test analysis, and exergy calculation of multifunctional adsorption systems using chemical adsorbent and different thermal transfer fluids

In the traditional adsorption cooling system, there are two main problems. One is its low coefficient of performance (COP). The other one is that it usually only can be used for cooling. A multifunctional adsorption system with CaCl2 and matrix is proposed to improve COP. Additionally, it can produce a cooling effect and electricity simultaneously. The authors compared twenty organics performance for the organic Rankine cycle firstly. Then they tested the adsorption cooling performance using different thermal transfer fluids. The results show that the COP, SCP (specific cooling power) can reach 0.23, 451.9 W/kg, respectively, and the overall exergy efficiency of the integrated system can rise from 0.14 to 0.25 due to the power generation of the organic and NH3 expansion power generation, when the waste heat source temperature, refrigeration temperature, and the cooling water temperature are about 103.2 °C, -16.1 °C, and 29.5 °C in the water system.

Impact of Weather Conditions on the Operation of Power Unit Cooling Towers 905 MWe

The paper presents the results of measurements and calculations concerning the influence of weather conditions on the operation of wet cooling towers of 905 MWe units of the Opole Power Plant (Poland). The research concerned the influence of temperature and relative humidity of air, wind and power unit load on the water temperature at the outlet from the cooling tower, the level of water cooling, cooling efficiency and cooling water losses. In the cooling water loss, the evaporation loss stream and the drift loss stream were distinguished. In the analyzed operating conditions of the power unit, for example, an increase in Tamb air by 5 °C (from 20–22 °C to 25–27 °C) causes an increase in temperature at the outlet of the cooling tower by 3–4 °C. The influence of air temperature and humidity on the level of water cooling ΔTw and cooling efficiency ε were also found. In the case of ΔTw, the effect is in the order of 0.1–0.2 °C and results from the change in cooling water temperature and the heat exchange in the condenser. The ε value is influenced by air temperature and humidity, which determine the wet bulb temperature value. Within the range of power changes of the unit from 400 to 900 MWe, the evaporated water stream m˙ev, depending on the environmental conditions, increases from 400–600 tons/h to the value of 1000–1400 tons/h. It was determined that in the case of the average power of the unit at the level of 576.6 MWe, the average values of the evaporation and drift streams were respectively 0.78% and 0.15% of the cooling water stream. Using statistical methods, it was found that the influence of wind on the level of water cooling, cooling efficiency and cooling water losses was statistically significant.

Experimental study on the parameter optimization and application of a packed-bed dielectric barrier discharge reactor in diesel particulate filter regeneration

To compensate for the shortcomings of the thermal and catalytic regeneration of the diesel particulate filter (DPF), a self-designed packed-bed dielectric barrier discharge (DBD) reactor for DPF regeneration was developed. The DBD reactor with the main active substance of nonthermal plasma (NTP) as the target parameter was optimized by adjusting the feed gas, packing particles (material or size), and cooling water temperature. Moreover, a set of optimal working parameters (gas source, O2; packing particles, 1.2–1.4 mm ZrO2; and cooling water temperature, 20 °C) was selected to evaluate the effect of different O3 concentrations on DPF regeneration. The research results showed that selecting packing particles with high dielectric constant and large particles, as well as reducing the cooling water temperature, with oxygen as the feed gas, contributed to an increase in O3 concentration. During DPF regeneration, the following changes were observed: the power of the NTP reactor decreased to lower than 100 W, the O3 concentration increased from 15 g m−3 to 45 g m−3, the CO and CO2 volume fractions of the particulate matter decomposition products increased, and the peak regeneration temperature increased to 173.4 °C. The peak temperature arrival time was 60 min earlier, indicating that the regeneration rate of DPF increased with the increase in O3 concentration. However, the O3 utilization rate (the amount of carbon deposit removed per unit volume O3) initially increased and then decreased; when the O3 concentration was set to 25 g m−3, the highest O3 utilization rate was reached. The packed-bed DBD technology contributed to the increase in the concentration of NTP active substances and the regeneration efficiency of DPF. It provides a theoretical and experimental basis for high-efficiency regeneration of DPF at low temperatures (<200 °C).

An experimental study of R-454C pull-down performance as a drop-in refrigerant in a walk-in cold store system

• Pull-down performance of R-454C in walk-in cold storeis experimentally investigated. • R-454C can replace R-404A in the existing walk-in cold store to complete its life time. • Compared to R-404A, compressor power decreases while COP increases using R-454C. • Product thermal load has the greatest impact on pull-down time and energy consumption. Walk-in cold stores represent the majority of commercial refrigeration applications for product cooling and freezing which make it the highest energy consumer in the sector. The present research aims to assess the pull-down performance of a cold store working with R-454C as a drop-in refrigerant for R404a under different product thermal loads and cooling water temperatures. The product thermal load was changed in a wide range of 0, 450W, 900W and 1350W while the cooling water temperature was changed in range of 27 to 33°C. Experimental results presented that the energy consumption increased approximately four times when the product thermal load increased three times from 450W to 1350W. Moreover, the system COP increases by 20% as the cooling water temperature decreases from 33 to 27°C over the presented cold store temperature. Although the system COP increased by 10.8% after switching to R454C, the system cooling capacity decreased by 12.6% and the energy consumption increased by 20.6%.

Performance analysis and simplified modelling of a capillary jet loop heat pipe

In this study, a prototype Capillary Jet Loop Heat Pipe has been tested to investigate its performances, and a lumped parameters simplified model has been developed to study the key parameters of the device. The tested Capillary Jet Loop is composed of an evaporator, a fluid loop with an ejector and a condenser. The working fluid used is R1233zd(e); an electric resistor of 40x40 mm2, dimensionally similar to a CPU, provides the thermal load, and a water cooling circuit removes it. An experimental investigation on the thermal behaviour has been conducted, varying the orientation, the thermal load from 40 W to 160 W, and the condenser cooling water temperature from 15 °C to 30 °C. The temperatures measured in different locations of the device have been used to estimate the equivalent thermal resistances. The results show a strong relation between performances and orientation and low dependence on thermal load and condensing temperature. The lowest equivalent thermal resistance value is obtained in the horizontal configuration with a value of 0.104 ± 0.005 K/W (CI 64%) at 80 W (5 W/cm2) while it reached the maximum value of 0.202 ± 0.002 K/W at 160 W (10 W/cm2) in vertical bottom heated orientation. The simulation includes a lumped parameter model focused on the two-phase evaporation condensation and capillary phenomena coupled with the fluid dynamics in the loop and in the ejector. Steady-state conditions are simulated. Under some simplified hypotheses, a parametric analysis was performed to investigate the influence on the thermal performances of the different construction and operative variables of the Capillary Jet Loop: loop length, tube diameter, ejector diameter, pore diameter, filling ratio, the fluid temperature. The maximum stable thermal load is calculated, and a stability map is found as a function of the fluid temperature. The matching point between the Loop and the ejector curve identifies the operating system point as a function of the studied parameters.

Transient optimization of annual performance of a photovoltaic thermal system based on accurate estimation of coolant water temperature: A comparison with conventional methods

One of the most critical parameters affecting the performance of a hybrid Photovoltaic Thermal (PV/T) panel is the coolant inlet fluid temperature. There are several approaches to estimate the water inlet temperature. This paper discusses the effects of an accurate evaluation of the actual temperature of the tap water that enters the system on the electrical efficiency and the optimal design of panels to maximize the electrical performance through a year. To accurately approximate the coolant water temperature, an approach based on the soil temperature at a depth of 1 m and theoretical and experimental data through a year in the city of Tehran, Iran, had been used. Eight design parameters had been selected to perform a sensitivity analysis; seven of them found to be effective on the electrical efficiency. Afterward, an optimization task utilizing genetic algorithm had been done. Finally, the performance of the design optimized based on the more accurate temperature of the water was compared with the performances of designs optimized based on the conventional temperatures of water. The annual results show up to 4.02% more electrical power generation versus models that approximate the inlet water temperature based on the ambient temperature.

Derivative‐Free Optimization of a Fixed‐Bed Methanol Synthesis Reactor

AbstractA one‐dimensional heterogeneous fixed‐bed methanol synthesis reactor model was developed for the optimization of carbon conversion and rate of methanol production. The developed model was validated both at pellet and reactor scales. The reactor inlet syngas composition and cooling water temperature, i.e., the design variables, providing the highest carbon conversion and rate of methanol production were determined by a constrained derivative‐free optimization algorithm. The results revealed that after optimization the carbon conversion was increased by 12 % and the rate of methanol production by 48 %. Under the optimized conditions, the stoichiometric number was in the range of industrial values.

Combine Harvester Cooling Water Temperature Prediction Based on CDAE-LSTM Hybrid Model

Cooling water temperature of the combine harvester during operations can reflect the changes of its power consumption and even overloads caused by extreme workload. There is an existing problem when extracting water temperature information from harvesters: data redundancy and the loss of time series feature. To solve such problem, a Convolutional denoising autoencoder and Long-Short Term Memory Artificial Neural Network (CDAE-LSTM) hybrid model based on parameter migration is proposed to predict temperature trends. Firstly, the historical data of the combine harvester are taken into account to perform correlation analysis to verify the input rationality of the proposed model. Secondly, pre-training has been performed to determine the model’s initial migration parameters, along with the adoption of CDAE to denoise and reconstruct the input data. Finally, after the migration, the CNN-LSTM hybrid model was trained with a real dataset and was able to predict the cooling water temperature. The accuracy of the model has been verified by field test data gathered in June 2019. Results show that the root mean squared error (RMSE) of the model is 0.0817, and the mean absolute error (MAE) is 0.0989. Compared with the performance of LSTM on the prediction data, the RMSE improvement rate is 2.272 %, and the MAE improvement rate is 20.113 %. It is proven that the adoption of CDAE stabilizes the model, and the CDAE-LSTM hybrid model shows higher accuracy and lower uncertainty for time series prediction.