Hot Fluid Temperature Research Articles

Thermodynamic, economic, and environmental performance comparison of typical geothermal power generation systems driven by hot dry rock

Hot dry rock has attracted broad attention due to its relatively high temperature and abundant resources. To match the power generation system suitable for low dryness hot dry rock geothermal fluid, this paper constructed four power generation systems: single stage flash system, double stage flash system, single stage flash combined organic Rankine cycle system and double stage flash combined organic Rankine cycle system. In the range of dryness 0∼0.3 and temperature 150∼200 °C, the matching characteristics between four power generation systems and geothermal fluids in hot dry rock with low dryness were studied. Taking the optimal net power output and exergy efficiency as objective functions, the performance of the four systems was optimized. In addition, the economic performance and environmental benefits of the system are compared. The results show that the temperature of hot dry rock geothermal fluid is positively correlated with the power generation performance, economic performance and environmental benefits of the four systems. In terms of power generation performance, the double stage flash combined organic Rankine cycle system has the best matching characteristics with geothermal fluids. For economic performance, double stage flash combined organic Rankine cycle system and double stage flash system have the highest matching degree when dryness is less than 0.1 and greater than 0.1, respectively. The environmental benefit of double stage flash combined organic Rankine cycle system is superior to the other three systems.

Review on the Performance Evaluation of Thermal Exchangers using Different Baffle Designs

The thermal performance of a heat exchanger depends upon various parameters like inlet temperature of hot fluid, type of hot fluid, type of cold fluid, the shape of baffles, the material of baffles, baffles angle, and property of ribs. Basically fluid flow and heat transfer characteristics largely depend upon the Reynolds number (Re). Reynolds number is basically the ratio of inertia force to viscous force. Re is only the factor by which we can decide whether the fluid is laminar or turbulent in shell and tube type of heat exchanger. The heat exchanger is an adiabatic device in which heat is transferred from one fluid to another fluid across a plate surface. In this paper, we have introduced some special types of triangular baffles with rectangular channels. The purpose of this apparatus is to enhance the performance of the heat exchanger. Heat exchangers, nowadays, are one of the most important heat & mass transfer apparatuses in industries like oil refining; heat treatment plants, electric power generation, etc. are long service life.

Recovery and effective utilization of waste heat from the exhaust of internal combustion engines for cooling applications using ANSYS

The exhaust gases from an internal combustion (IC) engine carry away about 75% of the heat energy which means only 25% of heat energy is operated for power production. A recovery unit at the exhaust outlet port can ensure heat exchange between different temperature fluids through conjugate heat transfer phenomena. This study represents heat recovery from exhaust gases that are emitted from IC engines which can be utilized in various applications such as vapor absorption refrigeration systems. In the present work, a new type of perforated fin heat exchanger for waste heat recovery of exhaust gases is designed using SolidWorks, and the flow field design of the heat recovery system is optimized using ANSYS software. Various parameters (velocity, pressure, temperature, and heat conduction) of hot and cold fluid have been analyzed. Inlet velocity of cold fluids including refrigerant (LiBr solution), water, and graphene oxide (GO) nanofluid have been adopted at 0.03 m/s, 0.165 m/s, and 0.3 m/s, respectively. Inlet velocity of hot fluid is taken as 2 m/s, 4 m/s, and 6 m/s, respectively, to develop a test matrix. The results showed that maximum temperature reduction by the exhaust is achieved at 104.8°C using graphene oxide nanofluids with an inlet velocity of 0.3 m/s and exit velocity of 2 m/s in the heat recovery unit. Similarly, temperature reduction by exhaust gases is acquired at 102 °C using water and 96.34 °C by using a refrigerant (LiBr solution) with the same exit velocity (2 m/ s). Furthermore, maximum effectiveness of 0.489 is also obtained for GO nanofluid when compared with water and the refrigerant. On the other hand, the refrigerant has the maximum log mean temperature difference from all fluids with a value of 224.4 followed by water and GO.

ANSYS simulation study of a low volume fraction CuO–ZnO/water hybrid nanofluid in a shell and tube heat exchanger

For the first time, the heat transfer performance of a CuO–ZnO (80:20)/water hybrid has been studied experimentally and numerically in a shell and tube heat exchanger under turbulent flow conditions nanofluid (STHE). All experiments are carried out with 0.01 ​vol% CuO–ZnO (80:20)/water hybrid nanofluid at Reynolds numbers (NRe) ranging from 1900 to 17,500. The stabilized hybrid nanofluids (30 ​°C-Tube side) are then used as a coolant to reduce the hot fluid (60 ​°C-shell side) temperature using a STHE, with the results for the convective heat transfer coefficient, Nusselt number, friction factor, and pressure drop reported. The primary goal of this paper is to investigate the impact of hybrid nanoparticle mixing ratio optimization on STHE heat transfer efficiency under various operating conditions. According to the findings, the CuO–ZnO (80:20)/water hybrid nanofluid improved the heat transfer performance of the STHE at all Reynolds numbers. When using nanofluid over water, the Nusselt number and pressure drop were improved by approximately 33% and 13%, respectively. The hybrid nanofluid's maximum thermal performance factor and thermal efficiency enhancement were 1.45 and 7%, respectively, at NRe ​= ​17,500. According to the study, the thermal conductivity of nanofluid varies by only 5% after ten trials. Furthermore, the ANSYS Fluent program was used to predict the behavior of the hybrid nanofluid in STHE, and the simulation results fit the experimental values very well.

Experimental study of single bed prototype adsorption refrigeration unit using waste heat energy

Adsorption refrigeration has more potential to become an attractive technology due to use of low-grade thermal energy and environmentally friendly refrigerants. Ammonia-activated charcoal pair based prototype of single bed adsorption cooling system was presented and tested. The most extreme measure of adsorption capacityof ammonia was found to be 0.22 kg/kg of activated charcoal, in shell and tube type adsorption bed respectively. This experimentation indicates that the cooling limit ranges from of 46.38 to 50.67 W, and thus the results show that it achieves a COP of0.0971 during a 62-minute total working cycle time under the condition of the temperature of hot fluid 120 °C, cooling fluid provided at the temperature of 30 °C, adsorption bed temperature of 40 °C and working pressure range up to 16 bar. The results have been represented by graphical relations. This unit of adsorption cooling is environment-friendly and has zero ozone depletion potential. The result indicated that the adsorption refrigeration system works effectively and is a better alternative to replacement for traditional refrigeration systems and the concept of a waste heat driven adsorption cooling system can be applied in the small cold storages.

First and Second Law Thermodynamic Analyses of Hybrid Nanofluid with Different Particle Shapes in a Microplate Heat Exchanger

The improvement in the quantitative and qualitative heat transfer performances of working fluids is trending research in the present time for heat transfer applications. In the present work, the first and second law analyses of a microplate heat exchanger with single-particle and hybrid nanofluids are conducted. The microplate heat exchanger with single-particle and hybrid nanofluids is analyzed using the computational fluid dynamics approach with symmetrical heat transfer and fluid flow analyses. The single-particle Al2O3 nanofluid and the hybrid Al2O3/Cu nanofluid are investigated for different nanoparticles shapes of sphere (Sp), oblate spheroid (OS), prolate spheroid (PS), blade (BL), platelet (PL), cylinder (CY) and brick (BR). The first law characteristics of NTU, effectiveness and performance index and the second characteristics of thermal, friction and total entropy generation rates and Bejan number are compared for Al2O3 and Al2O3/Cu nanofluids with considered different-shaped nanoparticles. The OS- and PL-shaped nanoparticles show superior and worse first and second law characteristics, respectively, for Al2O3 and Al2O3/Cu nanofluids. The hybrid nanofluid presents better first and second law characteristics compared to single-particle nanofluid for all nanoparticle shapes. The Al2O3/Cu nanofluid with OS-shaped nanoparticles depicts maximum values of performance index and Bejan number as 4.07 and 0.913, respectively. The first and second law characteristics of the best combination of the Al2O3/Cu nanofluid with OS-shaped nanoparticles are investigated for various volume fractions, different temperature and mass flow rate conditions of hot and cold fluids. The first and second law characteristics are optimum at higher hot fluid temperature, lower cold fluid temperature, lower hot and cold fluid mass flow rates. In addition, the first and second law characteristics have improved with increase in volume fraction.

Modeling of heat transfer of supercritical water in helical finned double pipe

Supercritical water (SCW) is a promising fluid for achieving high thermal efficiency. In the present work, the SST k-ω turbulence model is employed to numerically simulate flow and heat transfer behavior of supercritical water in horizontal double pipe with helical fins. Grid independence test was firstly carried out and then model was validated with experimental data. Different combinations of width, height and pitch in helical double pipe numerical model, width varying from 2 mm to 4 mm, height ranging from 2 mm to 6 mm and pitch available from 15 mm to 25 mm, were examined. In addition, effects of buoyancy force, hot fluid temperature and mass flux on the heat transfer performance were investigated. Buoyancy disturbs the flow field by inducing secondary flow. The flow field is symmetrically distributed on the tube-side. In contrast, the presence of the fins in shell-side breaks the symmetrical distribution and generates a swirling flow at the top of the fins. The results indicated that the peak tube-side and overall heat transfer coefficients emerged at hot fluid slightly greater than the pseudo-critical point temperature. Moreover, the overall heat transfer coefficient improved as mass flux on both the tube-side and the shell-side. However, the shell-side would induce a greater magnitude. Also, the shell-side pressure drop closely related to the shape factor and increased with it. The performance evaluation criterion for case 8 and case 9 were 2.08 and 1.88, respectively. Nevertheless, the pressure drop of case 8 was more than twice case 9. Consequently, case 9 may be an optimal configuration simultaneously considering the coupling effect of heat transfer and pressure drop.

Research of the Influencing Factors on Thermal Insulation Effect of Casing with Parasitic Pipes and Central Tubing

In the process of drilling in permafrost, the frozen soil is susceptible to melt under the influence of drilling fluid. To solve this problem, casing with parasitic pipes and central tubing was introduced to insulate the pipe from the permafrost. Then, a set of test system for the thermal insulation of casing with parasitic pipes and central tubing was designed to analyze its performance and influencing factors. The experiment reveals that the central part of the casing can effectively suppress heat transfer in the radial and axial direction and keep the outer wall at a low temperature. However, thermal insulation of the couplings on both sides are poor, which raise the outer wall temperature, resulting in a U-shape distribution of it. In addition, the sensitivity analysis and single-factor fitting of environmental and operational parameters indicate that the temperature rise from the environment and fluids will increase the outer wall temperature linearly, and the increase of drilling fluid displacement will reduce the outer wall temperature following a logarithmic relationship. From the coefficient of the multivariate fitting equation, it is clear that the most influential factor on outer casing wall temperature is the environmental temperature followed by cold fluid and hot fluid temperature. The research results show that using casing with parasitic pipes and central tubing to protect the permafrost is very feasible, and engineering technical measures such as lengthening the intermediate casing section, improving the coupling structure, maintaining low temperature and displacement of cold fluid can significantly improve the protective effect.

Effective utilization of CuO/water nanofluid potential in the natural circulation loop

Nanofluid potential in a rectangular natural circulation loop has been carried out through numerical investigation. A rectangular loop of dimension 110 cm length, 100 cm width in which 90 cm length of the heating and cooling sections is considered, respectively. The loop is filled with water-based CuO nanofluid with volumetric concentrations 1%, 2%, and 3%. Firstly, the validation of experimental results available in the literature is validated using the present numerical model. The potential of CuO nanofluids is utilized subjected to various inlet boundary conditions temperature and mass flow rate of cold and hot working fluids. The results show that CuO nanofluid can enhance the fluid flow and thermal performance of the loop. It is observed that heat transfer enhancement diminished with vol 3% because of dominating buoyancy forces. The study found that enhancement in heat transfer 5.33% and mass flow rate of 21.29% for CuO vol 2% nanofluid than water.

Effect of internal and external corrugated surfaces on the characteristics of heat transfer and pressure drop in a concentric tube heat exchanger

The main aim of the present work is to analyze the improvement of heat transfer through the simultaneous use of concave and convex inner and outer corrugated tubes within a concentric mini-tube heat exchanger. The purpose was to conduct a numerical study of the thermo-hydraulic characteristics of a concentric mini-tube heat exchanger with V-shaped corrugations, while considering different cases. In addition, hot water and cold water were used as working fluids. The simulations were performed for a countercurrent configuration, with mass flow rates of hot water and cold water ranging between 0.04 and 0.2 kg/s. The inlet temperature of hot fluid was set at 40 °C and that of cold fluid at 15 °C. The finite volume method was used to solve the mathematical model that allowed obtaining the temperature distribution, the heat transfer rate, as well as the entropy generation. These parameters were evaluated for different arrangements of the corrugated tubes. The results obtained showed that corrugations lead to improvement in the heat transfer rate due to higher exchange surface. A better average Nusselt number was also obtained from the arrangement of concave corrugated tubes with a phase shift angle of 180°.

α-Stirling hydrogen engines for concentrated solar power

α-Stirling engines are receiving more and more attention for applications of concentrated solar power in small power installations (15–30 kW). The design of these engines has not experienced in recent years the breakthrough needed to deliver close to the Carnot Cycle energy conversion efficiencies. The delivered efficiencies are limited to mid-to-high 20% in the typical installations “Dish Stirling”. Here we review the latest studies made on α-Stirling engines, unfortunately mostly based on theoretical models of limited reliability, but also including very few examples of Computer-Aided Engineering (CAE) modeling followed by prototyping and testing. Finally, we present in detail one CAE model of an α-Stirling engine delivering energy conversion efficiencies of 42% with hydrogen as working fluid and adopting one hot cylinder, one cold cylinder, and one regenerator, with the hot fluid temperature of 800 °C. This efficiency is much higher than current air microturbines, which may deliver efficiencies of only about 20% working at much lower temperatures.

Study the flow direction and number of tubes in cross-flow heat exchanger to improve the heat transfer coefficient.

This study deals with the effects the number of tubes and flow direction on the heat transfer coefficient. This investigation complete by study different lengths of smooth copper tubes (50,100, 150, 200 and 250) mm with different passes (2, 4, 6, 8 and 10) for cross flow heat exchanger to attain the best length to heat transfer numerically, by Solid work 2017 and ANSYS 16.1 program. The diameters of outer and inner tubes are (24 and 19 mm), air velocity (3 m/s), volumetric flow rate (5 L/min) and the inlet temperature of cold and hot fluid (25 °C and 80°C) respectively. Also been studying the effect of a smooth and triangle finned tube (4 passes) to enhance the heat transfer. Moreover, studying the effect of up and horizontal direction of the flow on heat transfer, by designing smooth tube 8 passes heat exchanger with the same dimension, air velocity inlet (1 m/s), volumetric flow rate (6 L/min), the temperature of the cold fluid inlet (22 °C) and the temperature of the hot fluid (50 °C). It can be noted that whenever the number of passes of tubes increases, the amount of heat transfer increase at the expense of the increase in pressure drop. The finned tube gives better heat improvement than a smooth tube and the direction of flow does not effect on the heat transfer.

Parametric Analysis of Shell and Tube Heat Exchanger

The present work investigated the effect of mass flow rate, hot and cold fluid temperature on total heat transfer and effectiveness for shell and tube heat exchanger. In addition, the effect of Reynolds number and type of fluid on heat transfer coefficient and effectiveness was studied. Increasing Reynolds number by 500 from 7000, 8% increasing in heat transfer coefficient has been observed. While 7% increase in Reynolds number, effectiveness has been increases by 5%. Nusselt number change shows higher effect on effectiveness for shell side as compared to tube side. A MATLAB program has been formulated to calculate the result by changing different parameters. During experimental observation, the rate of heat transfer is 143.74 kW and effectiveness of shell and tube heat exchanger is 0.50. The optimum heat transfer through shell and tube heat exchanger had been achieved at 0.0084 m2 surface area of tube and 27 number of tube.

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 and simulation study of forced convection in vertical eccentric annular space

In the petroleum production process, the tubing-casing annulus has been eccentric due to influence of gravity and thermal expansion, which complicates heat exchange. Forced convection heat transfer in vertical annulus with difference water-air ratios, eccentricities and radius ratios, has been experimentally studied with constant volumetric flow rate and temperature of hot fluid. The radius ratio that make Nu increase abruptly under operating conditions in this study is investigated numerically. The governing equations describing the heat transfer and flow are discretized using the Finite Element Method. Results indicate that the relation between Nu and radius ratio is non-linear. The radius ratios causing Nu to increase abruptly are 0.36 and 0.21 respectively. The coefficient of convection heat transfer increases as the radius ratios increase. For the eccentricity of 0.2, the decrease of water-air ratios enhances the heat transfer of eccentric annular space. For the eccentricity of 0.5 and 0.8, the heat transport first strengthens and then weakens with the decrease of water-air ratios. The effect of eccentricities on the Nu is affected by radius ratios and Re in the meantime. The empirical correlation is derived for the Nusselt number as a function of the Reynolds number, eccentricity and Prandtl number.

Numerical Simulation The Fluid Flow of a Triple Concentric Tube Heat Exchanger with Computational Fluid Dynamic (CFD)

Heat Exchanger (HE) is an important equipment in engineering application. It is widely used in many industries, such as automotive industries, power plant and food industries etc. This study aims focuses on Triple Concentric Tube Heat exchanger which it developed from double tube HE to know outlet temperature each fluid with Computational fluids dynamic method and then experimental study is used to validation for this study. It used for cooling water with the same fluid, in this research variation are inlet hot fluid temperature 50°C, 55 °C, 60 °C and mass flowrate 0.0249kg/s, 0,033kg/s and 0.041kg/s counter flow fluid.

Simulation Study on Efficiency of Woven Matrix Wire and Tube Heat Exchanger

Wire and tube heat exchanger has been utilized in refrigerators whose cooling performance depends on how much the wire are releasing heat. Wire efficiency is an important factor of the performance. The woven matrix is a new design of wire configuration on wire and tube heat exchanger. This research focused on optimization design of woven matix by varying wire pitch (pw 5,7,9 mm) and three inlet massflows with controlling the hot fluid temperature at 353K. Computational Fluid Dynamic Simulation is used to determine heat transfer distribution of fluid in tube. The validation was conducted experimentally by measuring 9 temperature points at heat exchanger. This research revealed that pw 7 mm with massflow rate 0.000571kg/s can decrease fluid temperature until it reaches 30oC with all wires working to release the heat and it results 74% wire efficiency. Then, pw 9 mm with massflow 0.0011kg/s has 64% wire efficiency, it was because the heat exchanger cannot decrease the fluid temperature to 303K. At high massflow, heat exchanger need more wire to decrease the temperature down to 303K. This research is recommended for cooling system widely applied in food industry, an optimal cooling system will reduce the cost of electricity consumption for cooler.

Thermal performance of corrugated plate heat exchanger using ethylene glycol as test fluid

This paper reports an experimental comparative thermal analysis of a flat plate heat exchanger and corrugated plate heat exchanger (CPHE) of different corrugation angles using ethylene glycol as test fluid. The experiments were carried out counter current mode using water as hot fluid at 75°C. Design of each plate provided with eleven thermocouple sensors to determine the temperatures, in which seven were used to measure the surface temperature of plate and four were used to measure the inlet and outlet bulk temperature of cold and hot fluids. The mass flow rate of test fluid, varied between 0.5 to 4 liters per minute and corresponding steady state temperatures is measured. Using experimental readings, temperature difference between the inlet and outlet streams (DT), logarithmic mean temperature difference (LMTD) and overall heat transfer coefficient (U) are determined. The obtained DT and U values of corrugation angles (300, 500) of CPHE were compared with those of flat plate heat exchangers. For corrugation angle of 30° and 50°, the DT and U values increases with increase of mass flow rate of the fluid.

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.

Geothermal Salt Factory (GSF) Design in Parangwedang Geothermal, Bantul, Special Region of Yogyakarta

Indonesia has the largest geothermal energy potential in the world with potential value ±28 GWe, but the potential of geothermal low enthalpy is still not utilized properly. On the other hand, improvement in the salt industry needs to be done because the salt industry in Indonesia has not been able to meet domestic salt demand. Domestic salt supply deficit is caused by the salt industry in Indonesia just relies on salt traditional farmers who are very dependent on the sunlight and the absence of a modern and sustainable salt-making industry. Therefore, the authors made a salt factory design using low enthalpy geothermal by utilizing Parangwedang geothermal as a heat source energy. Parangwedang geothermal is located in the Special Region of Yogyakarta with existence manifestation as a hot spring. Based on previous research, the potential of Parangwedang geothermal was 10 MWe. The reservoir rock may have a temperature range 115 °C and the hot spring fluid temperature 43 °C. The hot spring distance from the seashore is 403 meters with elevation reach 8 meters. The method used in this study is literature study and data collection in the field. Literature data is obtained from various sources and then compiled and grouped for the design of the salt factory that utilizes low enthalpy geothermal energy. This factory system will involve two pumps, one of which will drain the hot water from the Parangwedang hot spring and the other will drain the water from the ocean to the salt production pan. A boiling tank and condenser are used to boil the sea. Hot water from the boiling tank is used for drying the salt brine and brine is dried in the salt pan. In the result, the authors calculated factory production capacity, the GSF production capacity is ±14 tons salt each year.