It is known that today the cooling system of efficient air compressors that allows us to cool both heated compressor parts and the produced compressed air releases the heat to the environment. This heat can be used for common good, for example for the domestic water heating. Available cooling systems can conventionally be divided into the two types, in particular the air cooling system and the water cooling sys- tem. In the case of water cooling system it is possible to use the plate-typeheatexchanger. It is known that plate-typeheat exchangers are very compact and have a low hydraulic resistance at simultaneously high heat-exchange intensity. Today, we have an ample amount of de- veloped analytical methods used for the computation of heat exchange and hydrodynamics in the channels of plate-typeheat exchangers and the thermal state of such heat exchangers; however we are lacking of the research done using the tools of CFD-simulation. The authors made an attempt to determine the heat load and the hydraulic resistance of the plate-typeheatexchanger of a sectional type using the developed methods of CFD-simulation in the software environment of ANSYS-Fluent system. The simulation data were verified and compared with the computation data obtained using a known engineering technique used for the computation of the heat-hydrauliccharacteristics of plate-typeheat exchangers. The research data can be used for the heat-exchange intensification assessment and for the analysis of the flow to improve the efficiency of the plate-typeheatexchanger.
Low-grade Thermal Energy Conversion (LTEC) is a potential source of renewable energy. One of its forms is the Ocean Thermal Energy Conversion (OTEC) in which the temperature difference be- tween the warm surface water and the cold deep water of the ocean is utilized in driving a heat engine cycle. Unlike the conventional thermal power generation systems, the temperature differ- ence between the heat source and heat sink in OTEC system is relatively small. Therefore, efficient heat exchangers should be used since heat exchangers play a major role in the overall system performance and economics. Due to their efficiency even in operating at small temperature dif- ference, plateheat exchangers are strong candidates in OTEC systems. In this study, performance of a herringbone plate-typeheatexchanger is experimentally investigated. Moreover, numericalsimulation results obtained by using Fluent CFD software are compared with the experimental re- sults and found in good agreement.
Heatexchanger is an instrument used to transfer heat from medium of one fluid to another fluid. In this paper, an experimental setup for testing a chevron type brazed plateheatexchanger is utilized to investigate the thermal characteristics of the fluid. A numericalsimulation as carried out a local element-by-element analysis utilizing e-NTU method as employed for simulating the heatexchanger. In this approach, Nusselt number is expressed in terms of friction factor which in turn, is given as a function of chevron angle of the heatexchanger. The experiment is performed by using various no of plates, several fluid flow rate and inlet &outlet temperature values. The experimental results are validated to numerical result of a brazed platetypeheatexchanger. In a chevron typeplateheatexchanger looks like compactness, so increased the overall heat transfer coefficient of fluid as compared to normal platetypeheatexchanger. The main advantages of a chevron brazed typeplateheatexchanger as occupy less space and cost wise reduced and then increase the heat transfer coefficient of a fluid, though with increased pressure drop.
Fin-and-tube heat exchangers are frequently used in the process and HVAC&R industries which consist of a group of fins set parallel to one another at prearranged spacing. In level headed applications the principal thermal resistance for an air-cooled heatexchanger is usually on the air side which may account for 85% or more of the total resistance (Wang et al., 1997). In order to get better thermal performance and also to considerably reduce the dimension and weight of air cooled heat exchangers that is to improve the overall heat transfer performance, the use of enhanced surfaces is very well-liked in air cooled heat exchangers. (Kays and London, 1984) provide the most comprehensive design database though it is containing comparatively older information. Wavy or corrugated fins are exceptionally popular fin patterns that are urbanized to improve the heat transfer performance. It is advantageous to use wavy surface as it can lengthen the flow path of the airflow and thus cause better air flow mixing. As a result, higher heat transfer performance is expected compared to the other plate fin surface. In the present study wavy fin is considered for the determination of the performance in the fin-and tube heat exchangers.
In the conventional power plant, the coal combustion is still the major heat source. The air entering into the boiler may reach very high temperature by combusting with the pulverized coal. Simultaneously, the water is heated from the subcooled temperature to saturated temperature and boiling inside the tubes. In order to improve the thermal efficiency of the steam Rankine cycle, the saturated steam continues to be heated up to superheated steam in the superheater. Then, the steam will flow into the steam Rankine cycle for energy conversion. On the other side, the heat of the exhaust gas will be further utilized for preheating the water in the economizer. Afterwards, the temperature of the flue gas may decrease to 120°C, which should be further cooled down below 60°C in order to reduce the heat emissions to the environment. The primary surface heatexchanger (PSHX) is a kind of high-efficient and compact plateheatexchanger without any secondary heat transfer surfaces, which is generally recommended to be used as the recuperator or cooler in the gas turbine system. The following is a complete literature review of PSHX studies and the erosion simulation studies.
Plateheatexchanger can obtain higher thermal performance because of its advantages in high heat transfer coefficient, small scale, and can realize pure counter current flow. It has been widely applied in HVAC industry. In this paper, the numerical research of plateheatexchanger in solar heating system has been proposed. Aimed at the type of herringbone corrugated plate which has better thermal performance and been widely used, the three dimensional model is established by Gambit software. Using FLUENT software for nu- merical calculation, by studying the effect of corrugated inclination angle, corrugated depth, corrugated spacing and inlet velocity of heatexchanger on internal temperature, pressure, velocity distributions of domains, the rela- tionship between the above parameters and the Nusselt Number and the pressure drop was obtained by simulation data. Heat transfer coefficient and pressure drop correlations used to measure the overall performance of the heatexchanger. The result shows that the optimal structure parameters is corrugated angle 60˚, corrugated depth 4 mm and corrugated spacing 16 mm.
V. Kongkaitpaiboon et al.  reported an experimental investigation of heat transfer and turbulent flow friction in a tube fitted with perforated conical-rings. They have been investigated the influences of the PCR on the turbulent convective heat transfer (Nu), friction factor (f) and thermal performance factor (η) characteristics experimentally. The perforated conical-rings (PCRs) used were of three different pitch ratios (PR=p/D=4, 6 and 12) and three different numbers of perforated holes (N=4, 6 and 8 holes). The experiment conducted in the range of Reynolds number between 4000 and 20, 000, under uniform wall heat flux condition and using air as the testing fluid. It was found that the PCR considerably diminishes the development of thermal boundary layer, leading to the heat transfer rate up to about 137% over that in the plain tube. Evidently, the PCRs can enhance heat transfer more efficient than the typical CR on the basis of thermal performance factor of around 0.92 at the same pumping power. Over the range investigated, the maximum thermal performance factor of around 0.92 was found at PR=4 and N=8 holes with Reynolds number of 4000. The effects of the pitch ratio (PR) and number of perforated hole (N) on the heat transfer enhancement in a
Boonloi and Jedsadaratanachai (2014). They claimed that the V-baffle in the channel gives thermal enhancement factor around 4.25. Boonloi and Jedsadaratanachai (2016) numerically presented the discrete combined V-baffle and V-orifice in a square channel on convective heat transfer for Re = 5000 – 20,000. They detected that the increment on heat transfer rate is around 2.8 – 6.0 time higher than the plain channel. Gormaa et al. (2017) reported the enhancement of cooling characteristics for a triple concentric tube fitted with rib. The parameter optimization of a solar air collector with holes on baffle was reported by Hu et al. (2018). Li et al. (2018) simulated the thermal performance in a channel with multi V- baffle for turbulent flow regime. Menasria et al. (2017) numerically studied the thermo-hydraulic performance in a solar air heater duct fitted with novel rectangular baffle with high aspect ratio. They found that the Frontiers in Heat and Mass Transfer
ematic diagram of the experimental apparatus and the sharp edge version of the corrugated duct used in the heat transfer experiments are presented in Figs 1. The channel configuration is characterized by the corrugated channel height, the respective values of 10 mm. In the platetypeheatexchanger designed for 25 O corrugation angle and 31 mm plate pack length with 100 O C work temperature and design pressure 6 kg/cm 2 . The advanced technology of corrugated platetypeheatexchanger enhances the ransfer coefficient and its supports the system to improve the energy efficient and cost reduction.
closed-loop single-well solutions can prevent fracture clogging and fluid losses in porous reservoirs. Borehole Heat Exchangers
(BHE) or Deep Borehole Heat Exchangers (DBHE) aim to extract geothermal energy by circulating a working fluid in a well without producing geofluids or requesting injection processes, or result in thermal short-circulation between injection and production wells. Due to highly corrosive fluids at high thermal and pressure condi- tions, unexpected facilities failure may happen. Despite suggesting anticipated low efficiencies compared to the expectations from open-loop EGS, the risk-cost balance analysis coupled with a sus- tainability assessment could encourage a development of this tech-
should however also be applied to predict and study the supercrit- ical conditions present in very hot geothermal systems. CFD-based numerical techniques can provide an integrated and coupled well bore-reservoir heat transfer analysis tool for accurate geometrical designs and real working fluid compositions. As the fluid flow cal- culation over the whole length of a BHE is dependent on the bot- tom hole conditions where turbulence is present, it is expected that a CFD simulation will solve the heat and fluid flow equations more accurately than by using traditional 1D numerical or analyt- ical models.
In this paper, the field investigation on the frosting phenomenon was carried out to examine the heat transfer performance of ASHP in one of the typical cities, Enshi, a hot summer and cold winter zone of China. The results showed that the frosting phenomenon is serious in winter in hot summer and cold winter zone of China. The defrosting period of ASHP is irregular but most of the defrosting period is around 60 min. The COP of the ASHP was found to operate below 0.8. In order to analyze the heat transfer performance of fin tube heatexchanger, one experimental facility was designed and built to investigate the thermo-hydraulic performance of fin tube heat exchangers. The experiments were carried out with two different types of fin-tube heat exchangers, including plain fin tube heatexchanger and louver fin tube heatexchanger, at four different air flow rates. The basic tube surface temperature decreased with the running time and then kept relatively stable at a certain level after 70 min. However, the trend of variation of pressure drop was adverse to that of basic tube surface temperature. The pressure drop increased dramatically with the running time. Until 70 min, the pressure drop was kept near constant. Based on the findings about the thermo- hydraulic performance variation with running time, the defrosting period should be less than 70 min.
Abstract- After tubular heat exchangers, Plate-fin heat exchangers (PFHEs), are the most common types of heat exchangers in thermal engineering applications. Plate fin heat exchangers, because of their low weight, compactness and high effectiveness are widely used in cryogenic and aerospace applications. This paper focuses on the passive augmentation techniques in the recent past and will be helpful to designers implementing passive augmentation techniques in heat exchange instruments. For the compensation of the poor heat transfer properties, the surface area density of plateheat exchangers can be increased by making use of the secondary fins such as, triangular fins, off-set fins, wavy fins, louvered fins etc. In addition, for the enhancement of heat transfer a promising technique is the use of longitudinal vortex generators. Due to the pressure difference generated between the front and back surface of the vortex generator produces the longitudinal vortices. These longitudinal vortices facilitate the exchange of fluid near the walls with the fluid in the core and hence, the boundary layer get disturbed which causes the increase in temperature gradient at the surface which leads to the augmentation in heat transfer. An innovative design of triangular shaped secondary fins with rectangular or a delta wing vortex generator mounted on their slant surfaces for enhancing the heat transfer rate in plate-fin heatexchanger is proposed.
In the last few decades, to save energy and raw materials, and taking into account economic and environmental issues, many efforts have been made to build high-performance heat exchangers, and their primary purpose is to reduce the size of the system for a given heat load and increase the heat transfer capacity. An overview of the work done in this area can be divided into the following general methods: Passive methods that do not require external force; and active methods that need external power. Passive methods include the use of extended surfaces, compact heat exchangers, non- circular cross-sections, increasing the heat transfer by vortices, micro-channels, surface coating, surface irrigation, etc. Alternatively, mechanical stirring, rotating surfaces, fluid fluctuations, use of the electric field, injection and suction goes into active methods. Among the passive means of increasing heat transfer, the use of wavy channels due to the high increase in heat transfer and relatively low increase in pressure drop is of interest to researchers. The primary reason for enhanced heat transfer in the wavy channel is due to near wall recirculation flow. This recirculation flow exists at low Reynolds number. As the Reynolds number increases, the interaction between the core flow and near wall recirculation flow increases, and thus multiply the mixing behavior of this flow . When Reynolds number is significant enough to move the flow regime to turbulent flow, the destabilization of thermal boundary layer allows more interaction between the core and near wall flows.
The performance characteristics of cross flow plate fin typeheatexchanger for water-CMC and water-SA systems with different compositions are summarized in above tables 1 & 2. The overall heat transfer coefficients, surface temperature effectiveness, fin temperature effectiveness of cold and hot fluid and exchanger effectiveness are represented with respect to Reynolds’s number of cold and hot fluid.
Graduate School of Science and Engineering, Saga University, 1 Honjo-machi, Saga, 840-8502, Japan
In the present study, condensation and evaporation local heat transfer coefficients of the R1234ze(E) inside a brazed plateheatexchanger were investigated by using a test section which is combined with two grooved stainless steel plates. In the test section, wall temperature distribution was measured. The test section consists of eight plates; two of them were processed herringbone for refrigerant flow channel other two flat plates are set for cooling plate for refrigerant, and another consist on cooling water flow channel. In order to measure local heat transfer and temperature distribution, five thermocouples were set at not only flow direction but also in the right and left sides of plates. Local heat transfer coefficient and temperature distribution were calculated from wall temperature and local heat flux with downward and upward flow condition.
National institute of technology Rourkela Page | 13 Jamshidi et al. (2013) has experimental work on shell and helical tube heatexchanger to enhance heat transfer in helical tube section hot water is flowing and cold water is flowing on the shell side. The determination of heat transfer coefficient was done using Wilson plots. Taguchi method was used to optimise the coil diameter, pitch of the coil and shell side flow rate. He found out that coil diameter of helical coil, coil pitch and tube side flow rate are the most relevant parameters in helical coil heat exchangers. From the experimental works it was found that coil pitch affect the Nusselt number and this caused due to fluid flow rate. The high value for tube side Nusselt number is obtained for lowest coil pitch and high tube side flow rate this is caused due to higher torsion occurring for lower pitches. With the decrease in coil pitch the curvature of tube increases and strong secondary flow is produced in tube side which enhances the heat transfer. The tube side Nusselt number and overall heat transfer coefficient increases with increase in coil diameter of the tube.
However, various experiments showed significant heat transfer enhancement with little penalty of pressure drop in heatexchanger applications [3-6]. Carbon nanotubes (CNTs) have drawn extensive attention owing to their promising applications in various fields. One of the most important applications is employing CNTs as scaffolds of various oxides like TiO 2  to construct functional carbon-based hybrids or composites. Many methods including self-assembly, sol–gel coating , hydrothermal, solvothermal, and liquid/vapor phase deposition have recently been developed to prepare this kind of hybrids. Most of these methods are generally employed in aqueous reactive systems  where pristine hydrophobic CNTs require to be pre-oxidized in strong acids into their hydrophilic forms containing –OH and –COOH. However, the oxidization usually causes uncontrollable damage to the structure of CNTs , undesired surface defects and shortening of CNTs, which exerts adverse effects on the conductivity and mechanical properties of pristine CNTs. Therefore, it becomes important to develop new strategies for preparing uniform hybrids with pristine CNTs as starting supports .
In this project, we learned that by changing the dimensions of the heatexchanger, the heat transfer coefficient changes. This shows that the heat transfer coefficient is directly affected by the width of the slit and the diameter of the tube. The heat transfer coefficient needed for a process can be estimated when the outlet fluid temperature is given. This can be done by the simulation of Non-Isothermal Laminar Flow package in COMSOL Multiphysics with trial and error method. The outcome of this project is that we are able to compare the velocity and temperature profile of heat exchange with different dimensions (Nelson’s x=0.1, y=0.14; Vennesa’s x=0.14, y=0.1) at an outlet fluid temperature of 58℃. In the comparison for velocity field streamline in 2D, it is found that the velocity flow of water in the heatexchanger is more efficient when the length of y is longer as there are less dead zones which then allow more spaces for water to flow more. As for the velocity profile in 3D, the phenomena Vena Contracta is observed to have occurred in both heat exchangers. In this case, smaller diameter of the heatexchanger will oozes out the water at a higher velocity.
Abstract: In the present work computational fluid dynamics (CFD) was used to investigate the two phase cross flow of liquid nitrogen and gaseous nitrogen in tub-in-tube heatexchanger. The behaviour of the flow was investigated in heatexchanger along the entire tube length. The study has further been expanded to see pressure drop and heat transfer phenomena in two phase flow of liquid nitrogen. ANSYS CFX and FLUENT modules are used to get the required simulation results. Simulation results are in good agreement with the data.