Coil Heat Exchanger Research Articles

Experimental and numerical analysis of helical coiled heat exchanger

Bu çalışmada, helisel ısı eşanjörlerinin ısı transferi karakteristikleri sürekli şartlarda araştırılmıştır. Deneylerde soğuk suyun eşanjöre giriş sıcaklığı 20 °C, sıcak su sıcaklığı ise 50 °C olarak belirlenmiştir. Soğuk suyun debisi 2 – 3 – 4 ve 5 l/dk olarak ayarlanmıştır. Soğuk suyun eşanjörden çıkış sıcaklığı ölçülmüş ve iç taraf Nu sayısı hesaplanmıştır. Sayısal çalışma için eşajörün üç boyutlu modeli oluşturulmuştur. Hesaplamalı akışkanlar dinamiği paket programı (Fluent 18.2) kullanılarak eşanjördeki ısıl özelliklerin ve hız konturlarının belirlenmesi için sayısal analiz gerçekleştirilmiştir. İç taraf Nu sayısı ve soğuk suyun eşanjörden çıkış sıcaklığı deneysel çalışmada elde edilen verilerle karşılaştırılmıştır. Hesaplamalı akışkanlar dinamiği sonuçlarının deneysel bulgularla uyumlu olduğu tespit edilmiştir.

Optimization of inserted coiled tube three-fluid heat exchanger using genetic algorithms

The three-fluid heat exchanger is a multi-stream heat exchanger that provides three streams at different temperatures for certain usage objectives. Recently, optimizing heat exchangers generally and three-fluid heat exchangers especially have received great attention in the energy field. The current study objective is to get the optimal mass flow rate of the three streams to minimize the entropy generation number and maximize effectiveness. Optimization is performed on the inserted coiled tube type for 24 cases with different usage objectives and different mass flow rate constraints. The optimization is done using an analytical approach for the temperature profiles and a regressed model for the overall heat transfer coefficients. Single-objective and multi-objective genetic algorithms are the optimization algorithms. The result shows that cooling the hot fluid is the most efficient usage objective; however, heating the intermediate-temperature fluid is the less efficient usage objective. Also, the study shows that the entropy generation number is dependent on the mass flow rate constraint. The maximum effectiveness of 0.693 occurs when the usage objective is cooling the hot fluid. In this case, the mass flow rate of the cold and the intermediate-temperature fluids are maxima while the mass flow rate of the hot fluid is minimum. The minimum entropy generation number 0.0486 occurs when the mass flow rate of the cold fluid is maximum while the mass flow rate of the hot fluid and intermediate-temperature fluid are minimal.

Experimental Study on the Effect of TiO2–Water Nanofluid on Heat Transfer and Pressure Drop in Heat Exchanger with Varying Helical Coil Diameter

The growing demand for efficient heat exchangers has promoted extensive research in exploring advanced heat transfer fluids and novel geometries. This paper investigates the heat transfer and pressure drop characteristics in helical coil heat exchanger employing water-based TiO2 as nanofluid. The utilization of nanofluids offers promising enhancements in thermal conductivity and convective heat transfer in heat exchanger applications. The effect of nanofluid concentration and flow rate on heat transfer and pressure drop with varying helical coil diameter performance is investigated. Experimental tests were conducted using a heat exchanger with different helical coil pipe diameters of 9.53mm, 12.7mm and 15.88mm with constant pitch of 30mm and varying concentrations of TiO2 nanoparticles in water (ranging from 0.1% to 0.5% by volume). The heat transfer coefficient and pressure drop were measured at different operating conditions. The results shows that the addition of TiO2 nanoparticles to water significantly enhanced the heat transfer performance in the helical coil heat exchanger. There is an enhancement in heat transfer coefficient with increasing nanofluid concentration and with increase in pipe diameter. The maximum enhancement in heat transfer coefficient is observed at nanofluid concentration of 0.5% and for pipe diameter of 15.88 mm. However, there is increase in pressure drop with increase in nanofluid concentration and with decreasing pipe diameter. The pressure drop found to be higher for nanofluids compared to pure water. The maximum pressure drop is observed at a concentration of 0.5% and for pipe diameter 9.53mm. In conclusion, the use of a water-based TiO2 nanofluid in a helical coil heat exchanger offers improved heat transfer performance compared to pure water. However, the pressure drop also increases with nanofluid concentration and decreasing pipe diameter. Therefore, a trade-off between heat transfer enhancement and pressure drop should be considered in the design and operation of such heat exchangers.

Bibliometric Study of Double Pipe Helical Coil Heat Exchanger

Bibliometric Study of Double Pipe Helical Coil Heat Exchanger

A CFD investigation of the design variables affecting the performance of finned-tube heat exchangers

A wide variety of heating and cooling applications use heat exchangers. The increase in energy prices, the requirement for size reduction, and restriction on greenhouse gas emissions has led to the need for finding ways to develop efficient heat exchangers. A cost-efficient way to enhance the model of a heat exchanger by visualizing the effects of the design parameters is using Computational Fluid Dynamics (CFD). The reason for this exploration was to lead an examination of the varieties/changes in the general intensity move process for a Finned-Tube Heat Exchanger (FTHE), also known as Air Coil Heat Exchanger (ACHE) with a variety of plan boundaries like the quantity of tubes, course of action of tubes, and the material utilized for the intensity exchanger. The widely used heat exchanger that uses refrigerant R314a and air as the working fluids was simulated with different design modifications. The simulated results exhibited as to how the number of tubes, arrangement of coils/tubes, material of tubes, and density / spacing of fins, effects the pressure drop, temperature and velocities profiles, and heat exchangers’ transfer of a heat. The use of copper coils improved the heat transfer by approximately 61% as compared to aluminium coils.

Zeolite-coated fin–coil heat exchanger for CO2 recovery from simulated dry flue gas via low-temperature-heat-driven TSA

Adsorbent-coated heat exchangers are expected to achieve not only high adsorption and desorption rates based on the rapid heat transfer in their adsorbent layers but also a low pressure drop owing to their structured adsorbent layers. In this study, a CaA-zeolite-coated adsorber was experimentally investigated to improve the CO2 capture performance of low-temperature-heat-driven temperature swing adsorption (TSA) from dry flue gas, a major source of greenhouse gas emissions. At a feed CO2 concentration of approximately 10 vol%, a flow rate of 1 L-STP/min, and a temperature swing range of 20 °C–80 °C, the performance of the coated adsorbent was first compared with that of a heat exchanger of a similar volume packed with CaA zeolite pellets. Due to the enhancement in heat transfer of the coated adsorbent, almost the same CO2 concentration and a higher CO2 recovery ratio as those of the packed adsorbent were obtained at an appropriate cycle time despite that the amount of coated adsorbent was only one-third that of the packed adsorbent. Therefore, the accelerated heat transfer in the adsorbent layer significantly affected the increased mass transfer rate in or around the coated adsorbent. Next, the effect of the space velocity (SV) was investigated using a coated heat exchanger that had a three-times-longer length in the gas flow direction and approximately the same thickness of the adsorbent coating layer as the above coated heat exchanger. Although a separate discussion on the larger adsorber size is necessary, the CO2 recovery concentration was over 50% and the recovery ratio exceeded 80% as the SV was reduced by one-third. Furthermore, the fin pitch of the heat exchanger was doubled and the thickness of the adsorbent coating was doubled while maintaining the same volume of the heat exchanger and the same amount of adsorbent coating. This was done to reduce the heat capacity of the heat exchanger, which is a factor in heat loss in TSA, by reducing the number of fins used. The doubled adsorbent coating layer thickness and halved contact area with the gas flow resulted in a decrease in CO2 capture. Thus, the effects of an increased adsorbent layer thickness and a reduced contact area should be determined to further increase the effectiveness of the adsorbent-coated heat exchangers.

Innovative method for heat transfer enhancement through shell and coil side fluid flow in shell and helical coil heat exchanger

Innovative method for heat transfer enhancement through shell and coil side fluid flow in shell and helical coil heat exchanger

New Evacuated Tube Solar Collector with Parabolic Trough Collector and Helical Coil Heat Exchanger for Usage in Domestic Water Heating

Buildings represent approximately two-thirds of the overall energy needs, mainly due to the growing energy consumption of air conditioning and water heating loads. Hence, it is necessary to minimize energy usage in buildings. Numerous research studies have been carried out on evacuated tube solar collectors, but to our knowledge, no previous study has mentioned the combination of an evacuated tube solar collector with a parabolic trough collector and a helical coil heat exchanger. The objective of this paper is to evaluate the thermal behavior of an innovative evacuated tube solar collector (ETSC) incorporated with a helical coil heat exchanger and equipped with a parabolic trough collector (PTC) used as a domestic water heater. To design the parabolic solar collector, the Parabola Calculator 2.0 software was used, and the Soltrace software was used to determine the optical behavior of a PTC. Moreover, an analytical model was created in order to enhance the performance of the new model of an ETSC by studying the impact of geometric design and functional parameters on the collector’s effectiveness. An assessment of the thermal behavior of the new ETSC was performed. Thus, the proposed analytical model gives the possibility of optimizing ETSCs used as domestic water heaters with lower computational costs. Furthermore, the optimum operational and geometrical parameters of the new ETSC base-helical tube heat exchanger include a higher thermal efficiency of 72%. This finding highlights the potential of the heat exchanger as an excellent component that can be incorporated into ETSCs.

Pengembangan Alat Desalinasi Air Laut dengan Teknologi Thermal Energy Storage

The need for clean water in household life is very important because humans cannot live without it. The composition of seawater consists of 96.5% pure water and 3.5% other materials, namely salts, dissolved gases, and others. Indonesia is one of the countries that has the second-longest coastline in the world, so the potential for utilizing sea water is very large, one of which can be through the desalination process. Distillation itself is distillation, and its by-product is salt when seawater is heated using a heat energy source with a concentrated solar power (CSP) system. Based on research that has been done previously, the tool is a lab-scale seawater desalination device, but the process of making a lab-scale seawater desalination tool is not optimal. Then design the construction of a lab-scale seawater desalination device with the Multi Stage Flash (MSF) type, and the aim is to determine the performance and functionality of the MSF-type lab-scale seawater desalination device. The results show that the results of the coil heat exchanger development obtained an inlet temperature of 85.9°C and an outlet temperature of 67.8°C, and the room temperature in the chamber can be maintained at a temperature of 68.9°C. As for the components being developed, such as sea water pumps, hoses, tees, and sprayers, a sea water debit of 53.78 liters per hour has been obtained.

Experimental and numerical analysis of a CO2 dual-source heat pump with PVT evaporators for residential heating applications

Multi-source energy systems are a promising solution to lower the environmental impact of the heating and cooling sector and enhance the exploitation of renewable energy sources. In this context, dual-source solar-assisted heat pumps exploit solar energy and air as the low-temperature heat sources. However, the efficiency of solar-based systems is strictly related to weather conditions, location, and time. Therefore, there is a need for accurate models to be used in dynamic simulations of these systems and perform detailed performance analyses and study the involved energy flows.This paper presents an experimental and numerical investigation of a direct-expansion solar-assisted heat pump (DX-SAHP) operating with CO2 as the refrigerant. The heat pump prototype can work with an air-finned coil heat exchanger or photovoltaic-thermal (PVT) solar collectors as the evaporator. The solar-mode configuration allows the exploitation of the heat from solar radiation to evaporate the refrigerant and to improve the photovoltaic electricity production due to the cooling of the cells up to 8%.A numerical heat pump model, integrated with novel gas-cooler and PVT collectors models, has been developed and implemented as a TRNSYS type for dynamic simulations of the system. The model has been validated with continuous measurements during the heat pump operation in solar and air modes. The proposed model can be used for performing seasonal simulations of a heat pump operating with a transcritical CO2 cycle. Moreover, the outcomes of the analysis show how the configuration of a CO2 heat pump with a direct-expansion air-finned coil heat exchanger or PVT can be used to enhance the performance of the heat pump and increase the electrical efficiency of the photovoltaic cells.

A novel design for faster hydrogen storage: A combined semi-cylindrical and central return tube heat exchanger

Metal hydrides (MH) have recently attracted significant interest for hydrogen storage as they provide large storage capacity and a high degree of safety. The main disadvantage, however, is that storage speed is compromised by their low rate of hydrogen absorption. One possible way to accelerate the absorption reaction, and thus improve storage performance regarding incoming hydrogen transfer speed, is to increase the heat transfer rate inside the storage system. Among internal heat exchangers, using helical coil and semi-cylindrical coil heat exchangers significantly improves the heat transfer performance inside the storage system because of the secondary circulation. However, the central area of the storage system still has a lower heat transfer rate as this area is far away from the heat transfer fluid. For this purpose, the development of a heat exchanger structure is considered for the new achievement of this study. A semi-cylindrical coil heat exchanger incorporating a central return tube (SCHE-CR) is first developed from a semi-cylindrical coil heat exchanger (SCHE) to improve heat exchange rate at the MH central area. The tube size's effect on absorption is analysed. Further, a combination of internal and external heat exchangers is considered for further improvement of MH storage performance. The operating parameters of the heat transfer fluid for various heat exchanger configurations are investigated to determine optimal values. Results from numerical simulations indicate that absorption duration reduces by 30 % in the SCHE-CR case compared to the SCHE. Increasing the tube diameter of SCHE-CR results in a 40 % faster absorption reaction. Using SCHE-CR with a cooling jacket reduces the absorption duration by 51 % compared to the SCHE-CR. Among other operating conditions, the operating temperature of the cooling fluid is found to significantly affect the hydrogen absorption reaction with up to a 36 % enhancement of the absorption rate. However, the heat transfer coefficient between cooling fluid and MH, is not found to have a significant effect, as the improvement of the absorption rate is only 8 %. The new MH reactor configuration would be beneficial to improve heat exchange in MH storage applications.

Effect of annular ribs in heat exchanger tubes on the performance of phase‐change regenerative heat exchangers

AbstractOptimizing the efficiency of conventional heat exchangers is critical for improving the performance of various processes. This study proposed increasing the heat dissipation buffer space of heat exchangers by filling the gap between the heat exchanger and the shell with phase‐change materials for optimizing phase‐change heat exchangers. Comparative simulation analyses were performed by investigating the difference between the internal and external diameters of the inner ring ribs of the heat exchanger, the flow rate of the cooling liquid, the spacing distance, and the number of the inner ring ribs as independent variables. The results revealed that the heat transfer efficiency of heat exchangers can be improved by adding the inner ring rib structure to the heat exchange copper tube. The difference between the inner and outer diameters of the inner ring rib considerably influences heat dissipation. Furthermore, a sensitivity coefficient of 0.2457 can be obtained. The distance and number of inner ring ribs and the flow rate of cooling liquid exhibit certain effects on the heat transfer efficiency of the heat exchanger. The sensitivity coefficients were 0.1477 and 0.0935. The heat dissipation efficiency of the coil heat exchanger was improved by 3.8% by adding inner ring ribs in the coil heat exchanger channel.

Performance improvement for chilled water air conditioning cooling coils with various dimple fin geometries

The present research inspected the thermal and flow behavior of finned coiled tube heat exchangers in crossflow for chilled water air conditioning systems. The investigation variables cover the impacts of several variables, such as fin dimple shape, the number of fins, and the Reynolds number of water and air sides on the thermal-hydraulic aspects of a finned cooling coiled tube heat exchanger. The goal is to enhance this famous finned cooling coiled tube heat exchanger using dimples concerning the same coiled tube heat exchanger without dimples. Six test specimens were fabricated, three with fin dimple geometries as sharp-sided triangle dimples, curved-sided triangle dimples, and teardrop dimples. The other specimens with three different fin numbers 140, 155, and 170. The test runs were experimented in a transparent air duct with air Reynolds numbers ranging from 1540 to 6205, while the chilled water flow side has experimented with Reynolds numbers ranging from 3350 to 16250. The findings revealed that a higher Nusselt number and flow area goodness factor is achieved by a heat exchanger (D) with a curved-sided triangle fin dimple shape. The energy efficiency ratio for a cooling coil with a fin number of 170 is higher than that of cooling coils with fin numbers 140 and 155 by approximately 24.68% and 12.94%, respectively. Correlations of energy efficiency ratio, effectiveness, flow area goodness factor, and friction factor are extracted according to the experimental results with deviations.

Computational assessment of thermally stratified magnetohydrodynamics Maxwell nanofluid with Joule heating and melting heat transfer

Researchers have reported an excellent desire for power storage devices that are more reliable and long-lasting. Battery storage devices are used in waste-to-energy recovery, wind power, mixed energy generation, and heating reactor designs. There are three more helpful methods for storing heat energy: Latent heat storage, like sensible heat storage and chemical heat storage, is a type of energy storage. In these processes, latent thermal energy storage is quite expensive and productive. Melting is a technique for storing heat energy in a material. The substance is frozen to release the stored heat energy. Melting phenomena include freezing a ground-based pump’s heat exchanger coils, tundra melting, magma solidification, and semiconducting processes. Because of the importance mentioned above, the current study investigates the behavior of a two-dimensional Maxwell nanofluid with heat radiation influence across a stretchable surface. The melting process, quadratic thermal and solutal stratification viscous dissipations, and Joule heating effects will also be examined. The impacts of Brownian motion and thermophoresis diffusion will also be assessed. Moreover, the binary chemical reaction will be included when evaluating the MHD mixed convective flow. The governing nonlinear equations of velocity, temperature, and concentration of nanoparticles will also be used to form the constructed fluid model. Under the boundary layer approximation, the equations governing the problem are reduced into non-linear and dimensionless ordinary differential equations using appropriate transformations. The dimensionless governing equations are solved using the convergent approach. The Maxwell fluid parameter enhances while the magnetic field parameter decreases the velocity of the nanofluid, which is one of the most noteworthy findings of the study. However, when the Brownian motion and thermophoresis parameters increase, the fluid temperature increases. The decrease occurs in the concentration profile with improving solutal stratification estimations while growing with enhancing chemical reaction parameters. With the increase in nanoparticle volume fraction, the nanofluid’s temperature decrease, but the nanofluid’s velocity improves.

Field Study of Novel Storage Tank of Solar Water Heating System

In this paper thermo-hydrodynamic characteristics were investigated experimentally for a new type shell-helical coiled tube heat exchanger used as a storage tank of closed loop solar water heater system. Triple concentric helical coils were made of copper tubes of (12.5mm OD and 10mm ID) with coils diameter of (207, 152.2, 97mm) for outer, middle and inner coils respectively. The experiments were carried out during a clear sky days of (March and April 2012). The parameters studied in this work are: history of average temperature of shell side of the storage tank, collector heat gain, heat rejected from coils to shell side of the storage tank, collector efficiency, thermal effectiveness of the heat exchanger (storage tank), and pressure drop. These parameters were studied at four different circulating mass flow rates of (1.8, 3, 6, 9 l/min) and for two consuming modes of supply water namely no withdrawal, and continuous withdrawal of (1 l/min). The results show that stratification temperature in the storage tank is increased for no withdrawal compared with water withdrawal, also the shell side average temperature increases with increased solar time. Collector efficiency is increased with increasing circulation flow rates, also increases with water withdrawn from storage tank. The pressure drop decreases with the increase of solar radiation .

Stopped Flow of Glycerol Induces the Enhancement of Adsorption and Aggregation of HRP on Mica.

Glycerol is a usable component of heat-transfer fluids, and is thus suitable for the use in microchannel-based heat exchangers in biosensors and microelectronic devices. The flow of a fluid can lead to the generation of electromagnetic fields, which can affect enzymes. Herein, by means of atomic force microscopy (AFM) and spectrophotometry, a long-term effect of stopped flow of glycerol through a coiled heat exchanger on horseradish peroxidase (HRP) has been revealed. Samples of buffered HRP solution were incubated near either the inlet or the outlet sections of the heat exchanger after stopping the flow. It has been found that both the enzyme aggregation state and the number of mica-adsorbed HRP particles increase after such an incubation for 40 min. Moreover, the enzymatic activity of the enzyme incubated near the inlet section has been found to increase in comparison with that of the control sample, while the activity of the enzyme incubated near the outlet section remained unaffected. Our results can find application in the development of biosensors and bioreactors, in which flow-based heat exchangers are employed.

Novel multi-helical coil heat exchanger-based small-scale organic Rankine cycle: A detailed heat transfer analysis

This paper discusses a prototype of the ORC, which is developed utilizing a novel multi-coil evaporator and condenser for the waste heat source with a temperature below 100 °C. R123 acts as a working fluid for the ORC. The thermal performance of a multi-helical coil is evaluated experimentally and compared to the single-helical coil heat exchanger available in the literature.The performance of a novel multi-coil heat exchanger depicts that when the Reynolds Number varies from 60000 to 120000, the heat transfer coefficient varies from 1560 W/(m2K) to 2900 W/(m2K) for a single coil heat exchanger and 3014 W/(m2K) to 4531 W/(m2K) for multi helical coil evaporator. The Nusselt Number varies from 300 to 570 for single-coil heat exchangers and 715 to 1076 for multi-helical coil heat exchangers. The results show that the expander's power output is around 2.14 kW and proportional to the evaporator temperature and pressure increase. The high condensing temperature decreases the expander power output. The main contribution of the present work is developing a small ORC system with novel multi-helical coil heat exchangers and testing them on a lab scale for the most probable application to fulfill the electricity requirement in remote areas in the future.

Experimental investigation of heat transfer and effectiveness of employing water and ethylene glycol mixture based Fe3O4 nanofluid in a shell and helical coil heat exchanger

A shell and helically coil heat exchanger (SCHE) is used to experimentally investigate the performance of 60% water and 40% ethylene glycol mixture based Fe3O4 nanofluid as a coolant. Chemical co-precipitation was used for the synthesis of large quantity of Fe3O4 nanoparticles with an average particle size of 11.42 nm. Correlations for the thermo-physical properties of the nanofluid were developed. The exergy analysis and heat transfer characteristics pertaining to the heat exchanger were also investigated. The frictional exergy destruction is found to contribute together with heat transfer exergy destruction to the total entropy of the SCHE system. The exergy efficiency of the SCHE can be increased by 21% using 1.0 vol% of nanofluid, but the improvement becomes modest as the volume concentration is increased further. The NTU of SCHE is improved only by 2% over that of the base fluid at the flow rate of 6 lit/min because of the limited improvement of the overall heat transfer coefficient. Increasing the concentration of the nanofluid beyond 1.0 vol% shows a little improvement in the effectiveness of the heat exchanger. This study recommends that the volume concentration of Fe3O4/60:40 % W + EG nanofluid should not exceed volume concentration of 1.0% because the added benefit of working with concentrations higher than 1.0 vol% may not outweigh the added cost and complexities of the nanofluid.

Modeling and Simulation of Indirect Collector Solar Hot Water Heating System Based on TRNSYS

The use of solar energy is one of the important ways of clean energy heating in rural areas in the north, and the collector solar water heating system is an effective way to use solar energy. This paper takes a typical single residential house in a rural area of Shenyang as a research case to design an indirect collector solar hot water heating system. Based on the meteorological data of the winter heating period (November 1 - March 31 of the following year) in Shenyang, TRNSYS software was used to research the heat collection efficiency and scheme design of the heating system. The research results showed that: 1) The best material of the heat exchange coil of the hot water storage tank in the solar water heating system of the indirect collector is stainless steel with a thickness of 0.8mm; 2) The optimal installation angle of solar collectors in Shenyang is 55°; 3) The optimal area of the heat exchanger coil in the hot water storage tank is 4.40m2.

Numerical Study of Fan Coil Heat Exchanger with Copper Foam

Numerical Study of Fan Coil Heat Exchanger with Copper Foam