Hot Fluid Flow Rate Research Articles

Experimental thermal performance intensification of gravitational water vortex heat exchanger using hexagonal boron nitride-water nanofluid

One of the main concerns presently is the rapid improvement of thermal technology for widespread heat exchanger applications involving energy conservation and intensification of heat transfer process. For the enhancement of heat exchange processes, nanofluids have been considered as a potential substitute for conventional fluids, which in general have subpar thermal characteristics. Therefore, the present study focusses on the heat transfer enhancement and the intensification of overall thermal performance of the developed gravitational water vortex heat exchanger (GWVHE). The experimental investigation first involves the preparation and characterization of water-based hexagonal-boron nitrides (h-BN) nanofluids as well as the computation of thermophysical properties of different volume fractions of h-BN nanofluids. Subsequently, a comparative analysis evaluating the thermal energy exchange capabilities of water-to-water and water-to-h-BN nanofluids combination of two fluids has been conducted to investigate the intensification in thermal performance of the developed GWVHE. The experimental investigation is primarily based on calculating the thermal energy balance, overall heat transfer coefficient, log-mean temperature difference (LMTD) and the effectiveness of the developed GWVHE using effectiveness-NTU method. The experimental results reported that 0.02 % volume fraction of water-based h-BN nanofluids is more suitable for further testing of the developed GWVHE to mitigate the stability concerns at higher concentrations. The minimal thermal losses, that lie within the 10 % confirms the thermal energy balance and by using the h-BN nanofluids −to-water strategy for two fluids. The maximum value of heat exchange rate significantly increased from 8490 W to 9998 W with the utilization of h-BN nanofluids-to-water as compared to water-to-water combination. Furthermore, the maximum values of LMTD employing h-BN nanofluids are found to be reduced from 21.15 K to 17.53 K compared to the water-to-water combination confirming the intensification in thermal performance of GWVHE. The overall heat transfer coefficient values are also found higher when h-BN nanofluids are substituted instead of water. The maximum value of overall heat transfer coefficient for h-BN nanofluids-to-water combination is improved from 874 W/m2K to 1142 W/m2K compared to water-to-water combination. Moreover, by utilizing the h-BN nanofluids-to-water combination, the values of effectiveness are intensified by an average of 13.5 % and 9 % in both sets of testing parameters, respectively. All these maximum improvement in findings for heat exchange, overall heat transfer coefficient, effectiveness, and reduction in LMTD values are obtained by maintaining the inlet mass flow rate of cold fluid at 0.142 kg/s, while the inlet mass flow rate of hot fluid was varied in the range from 0.092 kg/s to 0.133 kg/s. Additionally, the inlet temperatures of hot and cold fluids are kept at 330 K and 296 K, respectively. Hence, the utilization of h-BN nanofluids is proven to be highly effective for boosting thermal energy exchange and enhancing the overall thermal performance of the developed GWVHE.

Experimental investigation and optimization of heat pipe heat exchanger performance under two distinct heat transport mediums through TOPSIS approach

This paper presents a comprehensive thermal performance analysis of the heat pipe heat exchanger by varying the input process parameters and optimizing the best condition for waste heat recovery through the TOPSIS technique. In this work, the heat pipe is constructed with a copper tube and segmented into evaporator and condenser sections carrying hot and cold fluids with a half-fill ratio. The heat pipe is oriented in 0° horizontally with the wick material made from stainless steel and works based on the capillary principle. The efficiency of the HPHE is evaluated by varying the input operational parameters, namely heat input, mass flow rate of hot fluid, inlet temperature of hot fluid, and mass flow rate of cold fluid, on response variables, specifically thermal resistance, energy balance ratio, universal heat transfer coefficient, and effectiveness. The experiment was designed for four factors at three levels as per Taguchi’s L27 orthogonal array, and the best optimising condition was determined by employing the multi-objective technique for order preference by similarity to ideal solution (TOPSIS) approach. The best input condition found was A3B1C1D3, in which the heat input was at 90 W, the mass flow rate of hot fluid was at 0.2 kg min−1, the mass flow rate of cold fluid was at 0.1 kg min−1, and the inlet temperature was at 60 °C. The effect of process parameters and their significance on output responses was analysed by executing an analysis of variance (ANOVA) statistical method. The mathematical regression model was generated, and validation was made to investigate the prediction error percentage.

Pengaruh Kenaikan Laju Alir Fluida Panas dan Arah Aliran terhadap Kinerja Plate and Frame Heat Exchanger

Plate and Frame Heat Exchanger (PFHE) is a plate and frame type heat exchanger that is efficient and effective in improving energy efficiency. Research using PFHE aims to determine the effect of increasing the flow rate of hot fluid on heat exchanger performance. This research was conducted at a flow rate variation of 0.7 L/min, 0.9 L/min, 1.1 L/min, 1.3 L/min, 1.5 L/min, 1.7 L/min, and 1.8 L/min with 180 seconds of testing each variation and recording data every 2 seconds. The cold fluid used is tap water and the hot fluid used is distilled water. The results showed that with the increase in hot fluid flow rate, the performance of PFHE also increased because the effectiveness of NTU (Ɛ-NTU) increased. The Ɛ-NTU value of unidirectional flow is 25.37% - 44.87% and in the opposite direction 37% - 68.39%. The largest Ɛ-NTU value in the countercurrent flow indicates that the countercurrent flow is more effective than the unidirectional flow. In addition, increasing the flow rate increases the Reynold's number (Nre) and Nusselt's number (Nu) which indicates the greatest convection heat transfer occurs at the highest flow rate.

Study the effect of hot fluid flow rate and carbon nanotube–water on the performance of nanofluid in gasketed plate heat exchanger

Study the effect of hot fluid flow rate and carbon nanotube–water on the performance of nanofluid in gasketed plate heat exchanger

Experimental comparison and numerical study of flow and heat transfer characteristics of the pipe rows in heat pipe heat exchanger

Lube oil cooling is a very important heat transfer process on board, and the use of liquid-liquid heat pipe heat exchangers (HPHE) is easier to maintain and save energy, and does not have the risk of leakage. In this work, the heat transfer and flow in the heat pipe row of liquid-liquid HPHE is analyzed. The numerical model of HPHE based on the thermal resistance network of heat pipe is constructed and verified with the actual experimental data, and its maximum deviation is 8.1%. Results show that increasing the working fluid temperature in the evaporative section improved the operating performance of the heat pipe inside the HPHE, with the maximum equivalent thermal conductivity reaching 7112 W·m−1·K−1 at 70 °C. Furthermore, increasing the hot fluid flow rate improved the heat transfer rate of the HPHE more than increasing the cold fluid inlet flow rate. The convective heat transfer performance equations were fitted to the HPHE, with reliable accuracy within 5% obtained for both the forced convection correlations in the condensing and evaporating sections. The pipe row effect was observed to have some variability, with the periodic variation of the heat transfer coefficient per pipe row being more pronounced. The heat transfer coefficient of the pipe row at the outlet decreased by 15.5%, and the heat transfer coefficient of the pipe row at the baffle gap was also about 15% lower than that of the middle pipe row.

Numerical investigations on a triple fluid heat exchanger with helical and sinusoidal coils

A modification is made in the existing concentric heat exchanger design to enhance its heat duty. A standard concentric tube heat exchanger is modified by considering two inner tubes with a combination of helical and sinusoidal coils. Numerical studies are performed in this triple fluid heat exchanger to assess its thermal performance by taking into account mass flow rate, fluid temperatures, heat transfer, which are governed by fundamental heat transfer equations. Computational fluid dynamics simulation methodology together with local and element-by-element method is applied with a MatLab computer code. Hot water and milk fluids are used as working fluids in helical and sinusoidal coils, respectively. Cooling water is used as shell side fluid. The attainment of high heat-load-per-unit-area and high surface-area-to-volume ratio is used as optimizing parameter in the simulations. The helical coil provides an increase in heat transfer rate and overall heat transfer coefficient increases by a percentage 13% for varying hot fluid flow rates, when it is compared with the sinusoidal coil. The pressure drop for the helical coil increases, exponentially compared to the sinusoidal coil, thereby it shows a higher pumping power for the helical coil.

Experimental Research on Heating Transfer Improvement of Materials that Change Phase in Tunnels in Cold Regions

In tunnel heating systems, phase change materials may minimize the consumption of conventional electric energy, which is very considerate in the field of tunnel heating in cold regions. Because of the phase change material’s poor heat conductivity, its annual growth rate heat absorption and release is slower; thus, the majority of phase change heat storage systems must improve heat transmission. In this study, a spiral metal ring is implanted in the paraffin to improve heat transmission to achieve this objective using a concentric sleeve-type paraffin heat storage device as a medium. Experiments were performed out in order to determine the effects of heating rate, hot fluid flow rate, and the use of a spiral metal ring on the heat storage and release process of a thermal storage device. In comparison to the paraffin thermal storage device, the embedding of the spiral metal ring accelerates the internal thermal performance of the composite heat storage device, resulting in a more uniform temperature distribution. When the thermal radiation heating rate is 60°C, 65°C, or 70°C during the heat storage process, the heat storage time of the composite heating storage device is reduced by 59.2 percent, 44.4 percent, and 40.7 percent, respectively. When the ambient temperature is 26°C and the heat storage device’s starting temperature is 65°C, the exothermic time is reduced by 22.6 percent.

Al-Biruni Earth Radius Optimization Based Algorithm for Improving Prediction of Hybrid Solar Desalination System

The performance of a hybrid solar desalination system is predicted in this work using an enhanced prediction method based on a supervised machine-learning algorithm. A humidification–dehumidification (HDH) unit and a single-stage flashing evaporation (SSF) unit make up the hybrid solar desalination system. The Al-Biruni Earth Radius (BER) and Particle Swarm Optimization (PSO) algorithms serve as the foundation for the suggested algorithm. Using experimental data, the BER–PSO algorithm is trained and evaluated. The cold fluid and injected air volume flow rates were the algorithms’ inputs, and their outputs were the hot and cold fluids’ outlet temperatures as well as the pressure drop across the heat exchanger. Both the volume mass flow rate of hot fluid and the input temperatures of hot and cold fluids are regarded as constants. The results obtained show the great ability of the proposed BER–PSO method to identify the nonlinear link between operating circumstances and process responses. In addition, compared to the other analyzed models, it offers better statistical performance measures for the prediction of the outlet temperature of hot and cold fluids and pressure drop values.

PERFORMANCE SIMULATION ON THE SHELL AND TUBE OF HEAT EXCHANGER BY ASPEN HYSYS V.10

Heat exchanger type shell and tube, which is the most commonly used heat exchanger in various industries. The efficiency of heat exchangers can be seen from their performance to affect its economy from a process. The purpose is to determine the influence of the hot fluid flow rate and the cold fluid on the overall heat transfer coefficient (U) and log mean temperature difference (ΔTLMTD) values. This simulation is done using Aspen HYSYS V.10 applications and obtained data of the total heat transfer coefficient (U) and ΔTLMTD values. The heat exchanger shell and tube used type 1-2 with single segment type 4 baffle, triangular tube layout, and shell length 1000mm. This simulation results in a hot fluid flow rate compared to reverse with the overall heat transfer coefficient and a cold fluid relative to the overall heat transfer coefficient, with the two best fluid flow rates at 2100 kg/h hot fluid and 1800 kg/h cold fluid at 10400 Kj/oC.h. The influence of the hot fluid flow rate on ΔTLMTD is relative to the straight, while the cold fluid flow rate is relative to the reverse, with the value of the second-best fluid flow rate at the 2100 kg/h hot fluid and the 1800 kg/h cold fluid at 26.25oC

Numerical and experimental study on thermal performance of a novel shell and helically coiled tube heat exchanger design with integrated rings and discs

Shell and Helically Coiled Tube Heat Exchangers (SHCTHEXs) are utilized in energy conversion applications in industry and in various engineering systems. They are generally composed of a helically coiled tube and a shell covering it. This coiled structure of tubes, provides better heat transfer and takes less space. There is an ongoing interest in research on this type of heat exchangers. In this study, a new design was created modifying a simple type of conventional shell and helically coiled heat exchanger, by integrating discs and rings. These rings and discs were attached to the helically coiled tubes with the aim of performing as baffles restricting the shell side flow and creating turbulence. The thermal performance of a conventional heat exchanger was improved by this modification. The study was carried out both numerically and experimentally. At first step, two SHCTHEXs, one conventional; one modified, were designed with same overall geometric dimensions. Then created solid models were numerically simulated with same boundary conditions using ANSYS Fluent. Simulations were performed with various flow rates and the results were reported. According to the simulations, compared to the conventional one, with the modified heat exchanger 7.1% increase in average amount of heat transfer rate and around 20% increase in overall heat transfer coefficient were obtained. With the promising results taken by simulations, the modified heat exchanger was fabricated with the same dimensions and it was experimentally tested with same conditions in laboratory to verify the simulation results. Experimental results were in harmony with the simulations with little differences. The average differences between simulation and experimental values in terms of average amount of heat transfer rate were obtained as 2.4% for 3 l/min hot fluid flow rate and 3.5% for 4 l/min hot fluid flow rate. Overall heat transfer coefficient of modified SHCTHEX with circular baffles achieved in the range of 1050–1400 W/m2K. General outcomes of this study exhibited successful design of baffled SHCTHEX.

Enhancement of heat transfer in shell and tube heat exchanger using mini-channels and nanofluids: An experimental study

This study aimed to experimentally investigate the effects of Al2O3-water nanofluids with six different volume concentrations (0.02%, 0.1%, 0.2%, 0.4%, 0.6%, and 0.8%) instead of water as working fluid on heat transfer and pressure drop on the tube side of a mini-channel shell and tube heat exchanger (MC-STHE). The shell-side hot fluid flow rate was kept constant at 180 L/h, while the flow rate of the tube-side cold fluids ranged from 125 to 600 L/h. The convective heat transfer coefficient (CHTC) of the nanofluids increased in the transition and turbulent regions. The nanofluids also extended the transition region. The nanofluids had higher friction factors than water. The nanofluids had an optimal volumetric concentration and a flow rate of 0.4% and 375 L/h, respectively, at which the CHTC enhanced by 49%, while the friction factor increased by 21% compared to water. Compared to macrotube heat exchangers, the CHTC enhanced 3 to 7 times with the combined effect of the mini-channels and nanofluids in the shell-and-tube heat exchanger (STHE). Consistent with earlier studies (maximum TEF of 1.8), the thermal enhancement factor (TEF) for the optimal volumetric concentration Al2O3-water nanofluid in the MC-STHE was 1.6 at most under the same hydrodynamic conditions. The performance evaluation criterion (PEC) and the efficiency evaluation criterion (EEC) showed that there was no point (not enhancement) in using nanofluids instead of the base fluid (water) in the MC-STHE.

Computational Fluid Dynamics Modelling and Analysis of Heat Transfer in Multichannel Dimple Plate Heat Exchanger

In the present study, Computational Fluid Dynamics is used for the heat transfer studies in the dimple, and flat plate heat exchangers. By employing water as a working medium (fluid), the same and different flow analyses were numerically studied. SOLID WORKS 2018 software was used for the study. The study primarily investigated the effect of the flow rate of hot fluid on the overall heat transfer coefficient. The study also analyzed the influence of hot fluid’s Reynolds number on cold fluid’s Nusselt number. It was observed that an increase in the mass flow rate of the hot fluid from 0.016 to 0.067 kgs-1 resulted in an increase in the heat transfer coefficient from 65 to 298 Wm-2K-1 for dimple plate heat exchanger (DPHE). Meanwhile, an increase in the Reynolds number of the hot fluid (from 200 to 1000), induced an increase in the Nusselt number of the cold fluid from 1.9 to 8.7 for DPHE. A correlation was developed to calculate the Nusselt number for the same flow analysis of the flat plate heat exchanger (FPHE). The study also compared the performance of the DPHE with that of the FPHE. The results of the same flow analysis indicated that the DPHE exhibited a Nusselt number value 39% greater than the FPHE at the highest mass flow rate of 0.067 kgs-1, while in different flow analysis, the DPHE demonstrated a Nusselt number value 41% greater than the FPHE at the highest mass flow rate of 0.067 kgs-1.

PERFORMANCE OPTIMIZATION OF COUNTER FLOW DOUBLE PIPE HEAT EXCHANGER USING GREY RELATIONAL ANALYSIS

Among various classifications of the heat exchanger, counter flow double pipe heat exchanger (CF-DPHE) is more suitable for many industrial heat transfer applications. In general, numerous research works are carried out to find optimal operating parameters for heat exchangers. In this study, grey relational analysis (GRA) is used to optimize the heat exchanger system output parameters such as the cold water outlet temperature (t2), the hot water outlet temperature (T2) and the effectiveness (ϵ). Such output parameters are the functions of the mass flow rate of cold fluid (mc), cold water inlet temperature (t1), the mass flow rate of hot fluid (mh), and hot water inlet temperature (T1). The application of this GRA method is capable of increasing counter flow double pipe heat exchanger effectiveness by 12.06%.

Performance analysis of heat transfer parameters in shell and tube heat exchanger with circumferential turbulator

Performance of heat exchanger is evaluated by the value of heat transfer coefficients, Reynolds number, Nusselt number, temperature distribution along the length, residence time and pressure drop. Improving these parameters for better performance is the main focus in designing the heat exchanger. In that view, helical coil gives more turbulence to the fluid flowing through it that leads to improved tube side heat transfer coefficient. For increasing the turbulence in cold flow, turbulators can be used in the circumferential area between helical coil and shell. In this work, heat transfer rate of shell and helical coil heat exchanger is improved by using circumferential turbulators. For the same mass flow rate of cold fluid different hot fluid mass flow rates (0.03 kg/s, 0.06 kg/s, 0.09 kg/s and 0.12 kg/s) were fixed for taking readings and the improvement is obtained by calculation of performance parameters. The temperature distribution along the length of the heat exchanger is plotted for different flow rates. Results show that, increasing the mass flow rate of cold fluid above the mass flow rate of hot fluid decreases the performance.

Machine learning algorithms for improving the prediction of air injection effect on the thermohydraulic performance of shell and tube heat exchanger

In this study, improved prediction methods based on supervised machine-learning algorithms is proposed to predict the effect of the application of air injection and transverse baffles into shell and tube heat exchanger on the thermohydraulic performance. The injection process is accomplished by injecting air into the shell with different flow rates to obtain the optimal thermohydraulic performance. Four different machine-learning algorithms have been employed to predict the thermohydraulic performance of the heat exchanger to avoid mathematical modeling or carrying out costly experiments. These algorithms are random vector functional link, support vector machine, social media optimization, and k-nearest neighbors algorithm. The algorithms were trained and tested using experimental data. The inputs of the algorithms were the cold fluid and injected air volume flow rates; while the outputs were the outlet temperature of hot and cold fluids, in addition to pressure drop across the heat exchanger. The inlet temperatures of inlet hot and cold fluids and volume mass flow rate of hot fluid are considered as constants. The obtained results demonstrate the high ability of the random vector functional link model to find out the nonlinear relationship between the operating conditions and process responses. Moreover, it provides better prediction capabilities of the outlet temperature of hot and cold fluids and pressure drop values compared with the other three investigated models in terms of performance statistical measures. The root mean square error and mean relative error for RVFL results is approximately one-third and one-fourth of that of SMO, SVM, or k-NN, respectively. The root mean square error was, 0.719167, 2.477069, 1.741808, and 1.855635 for RVFL, SMO, SVM, and KNN, respectively; while mean relative error was 0.016167, 0.061746, 0.043366, and 0.041383 for RVFL, SMO, SVM, and k-NN, respectively.

Experimental Study of Heat Transfer Rate in Single and Series Cross Flow Heat Exchanger using Matlab Coding

The present study investigates the heat transfer rate and effectiveness of cross flow heat exchanger by varying velocity and mass flow rate of the cold and hot fluids.The velocity of the cold fluid i.e. air varying from 15m/s to 30m/s(with an intermediate step of 20m/s and 25m/s) whereas the mass flow rate of hot fluid i.e. water is taken as 35lit/hr and 84lit/hr. The logarithmic mean temperature difference (LMTD) method is used to find the heat transfer rate. In thepresent workthe effectiveness and heat transfer rate werecompared between the single and series cross flow heat exchangers. The result shows an average increase of 47.14% and 59.59% of heat transfer rate analogous to mass flow rate of 84lit/hrand 35lit/hr

Effect of helical fins on the performance of a double pipe heat exchanger

Abstract In this work, the helical fins effect in the performance of a double pipe heat exchanger has been examined experimentally. The performance in terms of average heat transfer rate, heat transfer coefficient and effectiveness of heat exchanger in plain inner pipe is evaluated and compared with helical fins installed heat exchanger over inner pipe. In this experimental analysis, hot fluid flow rate is varied in range from 0.01 kg/s to 0.05 kg/s and hot fluid temperature at inlet is kept constant as 80 °C. The result shows the heat transfer coefficient is increased with introduction of fins. Average rate of heat transfer and effectiveness of heat exchanger are increased to 38.46% and 35% respectively at higher flow rate.

Performance Analysis of Heat Transfer Parameters in Shell and Tube Heat Exchanger with Circumferential Turbulator

Performance of heat exchanger is evaluated by the value of heat transfer coefficients, Reynolds number, Nusselt number, temperature distribution along the length, residence time and pressure drop. Improving these parameters for better performance is the main focus in designing the heat exchanger. In that view, helical coil gives more turbulence to the fluid flowing through it that leads to improved tube side heat transfer coefficient. For increasing the turbulence in cold flow, turbulators can be used in the circumferential area between helical coil and shell. In this work, heat transfer rate of shell and helical coil heat exchanger is improved by using circumferential turbulators. For the same mass flow rate of cold fluid different hot fluid mass flow rates (0.03 kg/s, 0.06 kg/s, 0.09 kg/s and 0.12 kg/s) were fixed for taking readings and the improvement is obtained by calculation of performance parameters. The temperature distribution along the length of the heat exchanger is plotted for different flow rates. Results show that, increasing the mass flow rate of cold fluid above the mass flow rate of hot fluid decreases the performance.

Experimental study of comparison in performance of heat exchanger with and without silicon dioxide nano particle used in cold fluid

In this experimental study deals about the comparison in between performance of heat exchanger with and without Silicon dioxide nano particle used in cold fluid. The common counter flow heat exchanger setup created with both hot and cold fluid as water. Hot fluid is maintained at the temperature of 170 °C by using electric heater. Cold fluid is in 30 °C as inlet temperature. There are individual temperature measuring thermocouples used in desired places of the experimental setup. There are four different mass flow rate considered for the cold fluid but the mass flow rate of hot fluid maintained as constant. The outlet temperatures of both hot fluid and cold fluid, heat transferred rate, effectiveness were measured and calculated experimentally for with and without Silicon dioxide nano particles used in cold fluid. These values were compared to identify the greatest values of experimental conditions.

Experimental Research on Heat Transfer Characteristics of Helical Coil Heat Exchanger with Varying Pitch for laminar Fluid Flow

To Study on rate of heat transfer in heat exchanger using helical coils has been studied by many researchers. There is less published literature available on varying pitch helical coil heat exchanger and detail characteristics of helical coil varying pitch by keeping constant curvature ratio considering heat exchange between fluid to fluid heat exchanger for laminar flow condition not available in the present available literature. Hence in present study three different coils with varying pitches are used to investigate the heat transfer characteristics of a Helical Coil Heat Exchanger. Hence coil of 25mm, 30mm, 35mm are used by keeping constant curvature ratio (=0.0667), experiment is conducted to study the influence of varying pitch on effectiveness, heat transfer rate, over all heat transfer co-efficient and Nusselt Number. The experiments is conducted in horizontal counter steady flow condition and changing the flow rate of hot fluid, pitch of helical coil heat exchanger. The results show that the varying pitch of helical coil heat exchanger has influence on heat transfer characteristics. The effectiveness of the helical coil heat exchanger is decreases with increase in mass flow rate of the hot fluid inside helical tube for varying pitch considered for study. The heat transfer rate of the helical coil heat exchanger is increases with increase in Dean Number of the hot fluid inside helical tube for varying pitch considered for study. The overall heat transfer coefficient increases with increasing hot water mass flow rate. The Nussult Number at different dean number increases for increasing helical coil pitch however the trend of average heat transfer rate for increasing M Number for varying pitch observed similar. By increasing the coil pitch of helical coil heat exchanger decreases Nussult Number, inside overall heat transfer coefficient, heat transfer rate and effectiveness.