Flow Water Temperature Research Articles

A Horizontal Distribution Model of Static Ice Cover Generated by Static and Dynamic Water Considering the Heat Transfer of Riverbanks

The thermal factor is the main reason for winter ice cover with a low Froude number flow, and the heat transfer to narrow and deep river banks accelerates ice cover formation and ice thickness change. The freezing of water flow to freezing thickening is a nonisothermal-flow phase transition process coupled with the water flow temperature, environment and riverbank. Here, the Nusselt number and viscous dissipation are used to consider the flow velocity influence on icing, and a thermodynamic model of static ice cover horizontal distribution considering riverbed heat transfer is established. The initial ice time, freezing time and static ice cover thickness formed by static and dynamic water calculated by the model were consistent with measured data. The model reflects the horizontal growth process of the static ice cover, which was significant for narrow and deep channels. The horizontal distribution of the static ice cover was thin in the center and thick on both sides. The maximum horizontal thickness difference of −20 °C indoor freezing for 24 h reached 15% of the central ice thickness. Compared with the degree-day method for calculating ice thickness, the numerical model and dimensionless formula better reflect the growth law and horizontal distribution characteristics of static ice cover and provide a theoretical basis for safe water conveyance under ice cover in winter and ice cover formation in reservoirs and lakes in cold regions.

Analysis of PV panels thermal control under different PCM properties

PCM thermo-fluid properties are significant in the cooling process, so researchers studied many types of PCMs. The integration of PCM in the PV active cooling technique increases the efficiency of the cooling system. The current study focuses on the selection of the PCM, which is integrated as a heat source for the active device. PCM melting temperatures and latent heat control the amount of heat transferred from PV panels, which affect the PV panels' output. So, the selection of a suitable PCM with suitable characteristics will increase the cooling system's efficiency. The analysis of simulation results to optimize the best PCM characteristics found that the RT25 PCM presents maximum PV output power and minimizes PV panel temperature. Otherwise, the best PV panel performance is achieved when the PCM melting temperature is close to the ambient air temperature and the PCM solidification temperature is close to the water flow temperature.

Effects of Different Heat Transfer Conditions on the Hydrogen Desorption Performance of a Metal Hydride Hydrogen Storage Tank

To investigate the influence of thermal effects on the hydrogen desorption performance of the metal hydride hydrogen storage system, a two-dimensional numerical model was established based on a small metal hydride hydrogen storage tank, and its accuracy was verified by the temperature variations in the reaction zone of the hydrogen storage tank during hydrogen desorption. In addition, the influence of the heat transfer medium on the heat and mass transfer performance of the hydrogen desorption reaction was analyzed. An external heat transfer bath was added to simulate the thermal effect of the model during the hydrogen desorption reaction. The temperature and type of heat transfer medium in the heat transfer bath were modified, and the temperature and reaction fraction variations in each zone of the hydrogen storage model were analyzed. The results showed that under heat transfer water flow, the reaction rate in the center region of the hydrogen storage tank was gradually lower than that in the wall region. The higher the temperature of water flow, the shorter the total time required for the hydrogen desorption reaction and the shortening amplitude is reduced. The variations in the temperature and hydrogen storage capacity during hydrogen desorption were similar, with water and oil as the heat transfer medium, under the same flow rate and heat transfer temperature, however, the heat transfer time and hydrogen desorption time of water were about 10% and 5% shorter than that of oil, respectively. When the air was used as the heat transfer medium, the heat transfer rate of the air convection in the channel was lower than the heat transfer rate of the tank wall, reducing the temperature difference between the air and alloy on both sides of the wall, decreasing heat transfer efficiency, and significantly prolonging the time required for hydrogen desorption.

Simulasi aliran dua fase pada campuran air-minyak di pipa horizontal dengan parameter termal

A CFD study of Water-Oil flow in the horizontal pipe was conducted using the VoF multiphase model coupled with the SST turbulence model scheme. This study aimed to simulate the mixture flow characteristic by takes account temperature parameter. It was numerically solved using a finite-volume model utilized in Fluent software. The simulation results compared towards experimental showed good prediction on the particular flow pattern. In this study, the thermal parameter was then solved by utilizing energy equation coupled by multiphase model. The water flow temperatures were varied in ranged of 300-340K. The results showed that temperature affected reducing the viscosity of the fluid as well ass the density. Furthermore, the flow pattern changed whereby oil was above the water due to its viscosity and density. This study is beneficial for accessing the temperature effect on the water-oil flow as represented in the applied petroleum industry of oil-lifting.

Study on the in situ performance of a 60 kW condensing gas boilers thermal installation and economic assessment

Condensing gas boilers currently represent the most advanced solution for heating based on combustion of fossil fuels from both efficiency and pollution points of view. Besides, compared with the district heating, condensing gas boilers make possible the entire management of the heat supply function by the real heating needs. Subsequently, minimization of the heating cost is possible. In this view, one of the buildings of the “Gheorghe Asachi” Technical University of Iasi was disconnected from the district heating and two condensing gas boilers – one of 25 kW and the other of 35 kW nominal output – were connected to the heating network to ensure the heat supply. A performance and economic analysis of the thermal installation with the two boilers, based on in situ experiments, was performed. The analysis was performed for nine operating regimes described by boilers flow water temperatures from 80 °C to 40 °C. Efficiency (in terms of higher heating value of the fuel) had varied from 86.7 % to 97.5 % and the price of thermal energy produced with the two boilers proved to be 21…30 % lower than the price of thermal energy coming from the district heating system. The annual heating savings are estimated to be 642…907 Euro/year, which induce a payback period of 1.6…2.3 years with strict reference to the investment represented by the two boilers.

Thermal effect and optimal design of cooling pipes on mass concrete with constant quantity of water flow

To study the heat transfer of pipe cooling process in concrete, an effective model combined with a radial basis function collocation method (RBFCM) is proposed. In this model, a replicable fictitious structure is imported that allows a set of fixed points to supersede the complicated adaptive remeshing or redistributing points, which significantly saves a lot of time and effort in the pre-processing of the numerical algorithm. Moreover, a relation between the mean temperature of water flow and the heat flux is derived from a heat balance equation. The validity of the proposed model is demonstrated in simulation of a typical three-dimensional problem. Numerical solutions are compared with those obtained by the finite element method and some experimental data. To find the optimum design, 32 cases involving 1 to 7 pipes under certain constraints are considered as follows: the quantity of water flow remains unchanged, the volume occupied by pipes keeps the same, and the same initial temperature of water is used for cooling. Since number, size, and positions of pipes are always changing during the design process, the ability of this approach is further illuminated. Finally, the effect of water flow with several conversing frequencies is investigated. As expected, the maximum temperature difference in concrete can be further controlled by enlarging conversing frequency. Numerical results reveal that the optimal design of pipe cooling system can not only minimize temperature, but also control temperature difference of the concrete structure. The process of design is useful for guidance of engineering practice to improve the structural safety and the economy of the whole building process.

PENGOLAHAN IKAN DI DAERAH ALIRAN SUMBER AIR PANAS BUMI DI DESA PAYO KABUPATEN HALMAHERA BARAT PROVINSI MALUKU UTARA

Potential geothermal water is located on the coast of West Halmahera Regency. The geothermal potential is utilized by the community as a medium of traditional medicine and local tourism. Utilization of hot water sources as a fish processing media has not been done. The purpose of this study was to determine fish processing using a modified oven in geothermal water flow. The research material is anchovy (Stolephorus indicus) measuring 10 cm. Fish drying equipment is made closed (airtight) as a whole. The process of fish maturation is done by laying the fish on the base located in the oven. The results showed that the fish cooked at room temperature 2 hours at room temperature 21 oC with geothermal water flow temperature 49oC-51 oC.

Method to improve performance of building integrated photovoltaic thermal system having optimum tilt and facing directions

A building integrated photovoltaic (BIPV) system can be installed at optimum tilt and orientation angle to maximize the electrical output. PV output is negatively correlated with the increase in the PV panel temperature. This paper aims at investigating the influence of water flow over the BIPV roof of a two-storied single-family house on the performance of the proposed optimally tilted semi-transparent BIPV thermal system having different facing directions. The periodic nature of insolation, ambient air temperature, BIPV cell temperature, slab temperature, water flow temperature and room temperature have been considered while solving energy equilibrium differential equations. The insolation values used in the energy equilibrium equations are computed employing periodic HDKR (Hay, Davies, Klucher and Reindl) model, which is based on anisotropic sky concept. Results indicate that the average BIPV cell temperature is reduced annually by approximately 10 °C and efficiency is enhanced by 6% when a water flow rate of 1.1 kg s−1 is provided over the BIPV roof. It is also observed that on the most critical day of the year, the temperature of outlet water is 11.5 °C higher than that of inlet water temperature which resulted in 4 kW extraction of exergy.

Decision support methodologies and day-ahead optimization for smart building energy management in a dynamic pricing scenario

Nowadays identifying techniques aimed at a rational use of electric power has become even more important than the production of energy itself. This is caused by different factors, as the progressive saturation of the electricity grid, which is increasingly subject to connection requests, mainly due to the development of plants which exploit renewable energy sources. This work suggests a new approach based on the combination of the optimizer and the simulator developed in the MATLAB/Simulink environment, in order to reduce the energy costs in buildings during the summer while taking into consideration the user comfort. The electrical consumption of the entire building is taken into consideration is here examined with the aim of applying an air-conditioning system. The goal is to find, the day before, which is the optimal hourly scheduling of the control variables that must be applied the next day, taking into consideration all external conditions; weather conditions and the hourly energy price. In order to achieve this objective, the control variables, that have been changed, are the room temperature set points and the flow water temperature set point. As required by the UNI EN ISO 7730:2006 standard, comfort measurement is calculated by PPD (Predicted Percentage of Dissatisfied) index. Different scenarios are investigated and two optimization algorithms are compared. The results show that there is an average of 10−28% potential cost saving, while maintaining a high level of comfort (PPD ≤ 12). The study is carried out by simulating a real office building in Italy, and the comparisons are shown regarding the actual settings applied to it.

Experimental Study on Energy and Exergy Analysis of a Counter Hollow Fiber Membrane-based Humidifier

The counter hollow fiber membrane-based humidifier is used for air humidification, which avoids the problem of liquid droplets carryover in traditional liquid humidification technology. In this study, an experimental rig was established for the hollow fiber membrane humidification system. The effects of air mass flow rate, air temperature, air relative humidity, water mass flow rate, water temperature on air humidity ratio increase, air temperature difference, power consumption per unit of humidification, humidification efficiency, energy efficiency, exergy destruction and exergy efficiency were experimentally investigated using the energy and exergy method. The results reveal the enhancement of the exergy efficiency with the increase in inlet air relative humidity, inlet air dry bulb temperature, air mass flow rate, and water mass flow rate. The results show that the humidification performance of the system is strongly influenced by the water temperature, while the humidification effect is more significant for the low temperature and low air humidity. It was found that as the relative humidity and dry bulb temperature of the air increased, the exergy destruction decreased significantly and the exergy efficiency increased. Increasing the air mass flow rate and water flow temperature resulted in an increase in both exergy destruction and exergy efficiency, while increasing the water flow rate had little effect on exergy destruction and fire efficiency. The exergy efficiency of the system ranged from 0.37 to 0.71. The maximum exergy destruction was 3.74 W, which occurred at air RHa,1=30%, air temperature Ta,1=30°C, water temperature Tw,1=28°C, and air and water flow rates of 32 kg/h and 7 kg/h, respectively. The humidification efficiency of the system ranged from 0.712 to 0.925, and the power consumption per unit of humidification ranged from 0.94 g/(h•W) to 12.50 g/(h•W).

Effect of water flow characteristics on gypsum dissolution

Gypsum is one of the karstic rocks with many positive and negative characteristics. The most important defect of these rocks is solubility against water flow. The dissolution phenomenon in gypsum is accompanied by the release of the sulfate ion in water increasing its concentration, gradually. In this research, the effect of water flow temperature (T), Reynolds number (Re) and water head (H) on gypsum dissolution rate was evaluated, experimentally. In all of the experiments, gypsum samples were prepared approximately in the same dimensions and a circular hole was created inside the sample. Results showed that by increasing the temperature above $ T/T_{a}=1.30$ (Ta = temperature of the ambient air), the dissolution rate of gypsum was significantly increased. At the end of the experiment, the hole diameter (d) at the temperatures $ T/T_{a}=1.09$, 1.30, 1.52 and 1.74 has been increased about 90%, 137%, 141% and 148% from the initial hole diameter (di), respectively. The dissolution rate at $ T/T_{a}=1.09$ is about 50% less than the dissolution rate at temperatures $ T/T_{a}=1.52$ to 1.74. Moreover, the increasing rate of the outlet discharge for H/d = 333 is 1.89 times the increasing rate of the outlet discharge for $ H/d=167$.

Numerical investigation on the performance and anti-freezing design verification of atomization equipment in an icing cloud simulation system

Aircraft icing occurs when flying through the cloud containing supercooled water droplets or ice crystals, posing a threat to flight safety. To simulate the natural icing environment, a climatic environmental test facility was designed, in which atomization equipment was utilized to spray micro-sized water droplets. To optimize and provide a reference design for the atomization equipment, a numerical study on its performance and anti-freezing design verification was carried out. The developed model was successfully validated with the maximum experimental ice thickness and its outlined shape on the test rod, with the error of maximum ice thickness at only 2.6%. The maximum deviation and mean deviation are at 1.13 mm and 0.68 mm, respectively. Freeze protection was finally enabled by ensuring the supplement temperature of the water, as well as the air in pipes, higher than 28.85 °C. Results suggested the best position for the test, at 2 m upstream of the nozzle outlet. The water flow temperature at the nozzle outlet was 29.45 °C higher than the freezing point. As a validated and applicable method, this study shows its novelty and practical value in the development of the climatic environmental test facility.

Effects of Different Temperatures on the Softening of Red-Bed Sandstone in Turbulent Flow

The rates of chemical reactions are highly dependent on temperature, meaning that the actual geological rock mass is affected by different temperatures. Only when the temperature effect is considered can the mechanism of the influence of temperature on the interaction between water and rock be further understood. It was found that the condition of turbulent flow is more likely to promote the softening of red-bed sandstone than the conditions of laminar flow and static water in an experimental study on the softening effects of different flow patterns on red-bed sandstone. Therefore, based on a multi-functional self-circulating open channel hydraulic test system, this paper designs and completes equal volume saturated tests of red-bed sandstone at low temperature (1 °C), medium temperature (23 °C), and high temperature (45 °C) under the turbulent conditions of three equal temperature gradients. The chemical action of the circulating solution in water flow at different temperatures, the propagation of micro-cracks in rock and the changes in mechanical indexes are discussed. The influence laws and mechanisms of the different temperatures on the softening of red-bed sandstone in turbulent flow are revealed. The results show that low-temperature flow can inhibit the softening of red-bed sandstone in the range of 1–45 °C. With the increase in water flow temperature, the development degrees of micro-structures and the mechanical damage of the corresponding rock become more notable. That is, temperature affects the physical and chemical water-rock interactions and then changes the internal structure of rock, thus affecting the softening and failure processes of red-bed sandstone. The study provides a theoretical basis for the further investigation of the softening laws and mechanisms of other red layered soft rocks by temperature under turbulent conditions.

Numerical Simulation of Transient Temperature Field of Single Fissure Flow in Mining Rock Mass

In this paper, the transient temperature field distribution of single fissure water flow is studied in order to study the fluid-solid coupling heat transfer mechanism of the rock mass. By simulating the flow state of underground water flow along single fissure of rock mass, it establishes the seepage model of single fissure. In addition, the mathematical model of temperature field under the influence of seepage field is established by simplifying the equations of single fissure and temperature control. The results show that the heat balance is closely related to temperature difference and time under fluid-solid coupling, and the greater the change of permeability velocity, the greater the change of temperature distribution. With the increase of time and heat transfer, the temperature difference between the water flow temperature and the wall surface of the rock mass gradually decreases, and the temperature isograde change rate along the flow direction of the water flow decreases gradually.

A multifaceted analysis of the relationship between daily temperature of river water and air

The aim of the study was to establish the strength and direction of the relationship between daily temperature of river water and air with the use of selected estimation methods. The relationship was assessed for the River Noteć and its tributaries (Western Poland), using the cross-correlation function and Granger causality. The study established cause-and-effect relations for “water–air” and “air–water” directions of influence. It was confirmed that forecasting the pattern of flowing water temperature from changes in air temperature yields better results when done based on data from the previous day. Results of modelling the relationship between data series with the use of the linear and natural cubic splines models confirmed the presence of a nonlinear relation. It was also established that there is a statistically significant correlation of random fluctuations for both temperature series on the same days. This made it possible to confirm the occurrence of short-term connections between water and air temperature. The results can be used to determine the qualities of thermal regimes and to predict temperature of river waters in the conditions of climate change.

The prediction of heat efficiency and pollutant emission of non-rated loaded condensing heat exchangers

In order to study the working conditions of condensing heat exchangers under non-rated load conditions, the orthogonal test method was conducted on the condensing gas water heaters by experiment firstly in this paper. Eighty groups of the experimental data about the relationship between the design variables and the object functions were obtained, among them, the design variables include excess air coefficient, flue gas flow, water flow and water flow temperature, and the objective functions include heat exchanger efficiency, NOx and CO emission concentration. The above experimental data were divided into two groups for the training and prediction of neural networks. Here two neural networks of BP artificial neural network (BPNN) and generalized regression neural network (GRNN) will be used to predict the heat efficiency and pollutant emission of condensate heat exchanger at partial load rate. The results show that both BPNN and GRNN structures achieve the required prediction accuracy, and the prediction accuracy of GRNN is higher than that of BPNN. The condensing heat exchanger can achieve higher heat exchanger efficiency and lower concentration of NOx and CO emission at the 90–100% load rate. When the load rate is lower than 30% or higher than 100%, the heat efficiency of the heat exchanger is decreased, and the concentration of pollutant emission is increased rapidly.

Development of a calorific value controller using bimetal fin channel for PCM heat storage

This paper reports on the development of a new type of heat exchanger with bimetal fins for controlling the calorific value of water through phase change material (PCM) heat storage. It presents detailed numerical and experimental data on the velocity and temperature of water flow in a channel equipped with bimetal fins on the wall. Computational fluid dynamics and particle image velocimetry are used to analyze the flow behavior around the bimetal fins. The bimetal fins increase the insulation performance at the wall, such that the heat loss rate is decreases by a maximum of 56%. Furthermore, the flow rate and calorific value can be controlled at 10 L/min and 50 kJ, respectively. Consequently, the discharging-time during which hot water can be generated increases by a maximum of 70 min.

Investigation of a Novel Mechanical to Thermal Energy Converter Based on the Inverse Problem of Electric Machines

A novel converter that can directly transform electrical, wind, hydraulic and other types of mechanical energy into thermal energy is presented in this study. First, the thermal energy of the converter is classified and then calculated by a finite element method. The eddy current distribution in the stator of the converter is also discussed. Second, the temperature field of the converter is calculated using a boundary element method. Subsequently, a thermal power–temperature coupled calculation method is presented to calculate the actual thermal power and temperature of the converter. The characteristic curves of the actual thermal power and the increase in water flow temperature are then presented based on the calculation results. Lastly, an experimental system is built, the thermal power and temperature of the converter are measured and the experimental results and the analytical calculations are compared.

Experimental study of a diesel engine heat pump in heating mode for domestic retrofit application

An engine driven heat pump (ENHP) can provide better efficiency compared to electric heat pump (EHP) considering primary energy consumption. The present work aimed to find suitability of diesel engine heat pump as a domestic retrofit application for off or weak gas/electricity network area. For this work, water-to-water heat pump test facility was developed which consisted heat pump, diesel engine and heat recovery arrangements. The system performance was evaluated for 65 °C flow temperature from condenser at three different engine speeds (1600, 2000 and 2400 rpm) and four evaporator water inlet temperatures (0, 5, 10 and 15 °C). The system performance was evaluated by heating capacity, isentropic efficiency, coolant heat recovery, exhaust gas heat recovery and PER. Performance analyses showed that heat recovery contributed 33% in total heat output where heat recovery was in a range of 1.7 to 3.7 kW. PER varied in the range of 0.9 to 1.4 showing good potential in terms of 35–65% primary energy saving and 23–42% CO2 emissions reduction compared to conventional systems. DEHP optimisation showed ability to meet water flow temperature requirement of 65–73 °C by speed variations and heat recovery providing good potential to meet heating demand during winter and summer periods in retrofit settings.

Heat exchange model in absorption chamber of water-direct-absorption-typed laser energy meter

Abstract The interaction between laser and water flow is very complicated in the absorption chamber of a high energy laser (HEL) energy meter which directly uses water as an absorbing medium. Therefore, the heat exchange model cannot be studied through traditional methods, but it is the most important factor to improve heat exchange efficiency in the absorption chamber. After the exchanges of heat and mass were deeply analyzed, experimental study and numerical fitting were brought out. The original testing data of laser power and water flow temperature at one moment were utilized to calculate those at the next moment, and then the calculated temperature curve was compared with the measured one. If the two curves matched well, the corresponding coefficient was obtained. Meanwhile, numerous experiments were performed to study the effects of laser power, duration, focal spot scale, and water flow rate on heat exchange coefficient. In addition, the relationship between water phase change and heat exchange was analyzed. The heat exchange coefficient was increased by optimizing the construction of the absorption chamber or increasing water flow rate. The results provide the reference for design of water-direct-absorption-typed HEL energy meters, as well as for analysis of the interaction between other similar lasers and water flow.