Tube Spacing Research Articles

Simulation of the Optimal Refrigerated Floor Design for Ice Rinks

A good design of the ice rink floor could save a great deal of capital and operational costs for hockey arenas. This ice rink floor design focuses on a cost-effective tube arrangement and an optimal concrete coverage over the tubes that could provide sufficient heat transfer rate between the coolant and the freezing ice. This paper reports a theoretical model to simulate the heat transfer characteristic of a different tube diameter, spacing distance, and thickness of the concrete coverage of the tubes of an ice rink. In addition, calcium chloride and ethylene glycol with water solutions are compared to figure out the pros and cons of these two secondary coolants. This model prediction is compared to the typical ice floor arrangement in order to determine the best floor construction scenario.

Experimental study on the distribution of local heat transfer coefficient of falling film heat transfer outside horizontal tube

An experimental system was built up to measure the outer circumferential distributions of the local heat transfer coefficient of horizontal tube falling film flow. The wall temperature along the angle were measured. Based on the experimental data, the local heat flux distribution on the tube surface were obtained by numerical calculation. The local heat transfer coefficient distribution outside the tube were obtained. The effects of spray density, tube spacing, average heat flux and fluid temperature on local heat transfer coefficient were investigated. The results show that the local heat transfer coefficient decreases sharply with the increase of angle, then decreases steadily, and finally increases slightly. According to the distribution of the local heat transfer coefficient and heat transfer mechanisms, the tube surface is divided into the impingement zone, the heat diffusion transfer zone and the tail detachment zone. The increase of spray density has little influence on the heat transfer in the impact zone, but make the heat transfer increases slightly in the heat diffusion transfer zone and the tail detachment zone. The influence of tube spacing is mainly concentrated in the impingement zone. The heat transfer is enhanced with the increase of tube spacing in the impingement zone. The average heat flux has no obvious effect on heat transfer. With the increase of fluid temperature, the heat transfer is greatly increased all over the cycle. Besides, based on the experimental data, new correlations of local heat transfer coefficient of falling film flow outside a horizontal tube are proposed.

Electric Arc Recoil–A Novel Method for Reducing Lightning Strike Potential Difference for Transmission Line

Increasing arc pressure by tens of times with fine pouring tube, a positive shock wave by the pouring arc entering the closed space of the thin tube (electric arc recoil wave). The pressure of electric arc recoil wave is 8 to 23 times than that of the arc tube pouring wave. Since the recoil wave has more pressure than the arc tube pouring wave, and their directions are opposite, the tube poring arc is driven away from the tube channel by the recoil wave. The arc completely emptying and a large scale truncation to the electric arc are formed. Therefore, the truncation arc interrupts the lightning current, and recombusts to form a new tube pouring wave and backwash wave. The arc truncation and recombustion are caused by arc tube pouring and electric arc recoil alternately, and forming the intermittent lightning discharge, a large decrease in the amplitude of lightning current, steepness and discharge time. The results show that the amplitude of lightning current can reduce from 67.14 kA to 35.1 kA, and the lightning current steepness can decrease 77.3%. This attenuation method of lightning current amplitude could significantly reduce the lightning current flowing into the ground, the induced overvoltage and the ohm potential difference. Additionally, the problem of lightning strike step voltage in high soil specific resistivity areas and electromagnetic induced overvoltage can be solved by the method in this paper. The probability of original fault is reduced, and the operation reliability is enhanced. The method can lower the cost of ground network and improve the lightning protection performance.

Numerical Study on Optimal Scheme of the Geothermally Heated Bridge Deck System

Ground source deicing system application in bridge decks is an alternative to salt use, which reduces corrosion and extends the deck service life. Herein, a preliminary parametric numerical analysis is performed to investigate the effects of several important parameters (tube spacing, inlet temperature, flow rate, and concrete cover) on heat transfer performance. Three evaluation indexes (average top surface temperature, snow melting proportion, and heat absorption power) are introduced, and a synthetic evaluation index is proposed to comprehensively consider factors. Mainly referring to the synthetic evaluation index, the optimal design scheme of a geothermally heated bridge deck system under various conditions (layout, lane number, ambient temperature, and tube spacing) is obtained and analyzed to determine the optimal inlet temperature and guide heated bridge deck design. Finally, the influence of wind speed and two adjustment methods are studied. The results indicate that the horizontal layout is the recommended circulating tube layout. The established empirical equations reveal that the optimal inlet temperature is linearly related to ambient temperature and exhibits a quadratic relationship with tube spacing. There is no need to add a heat insulation layer at the bridge deck bottom, and only tubes arranged near the wheels in lanes are recommended.

Numerical simulation of an atmospheric pressure plasma jet with coaxial shielding gas

A two-dimensional (r, z) numerical simulation of the discharge characteristics of an atmospheric pressure plasma jet (APPJ), with coaxial shielding gas, was performed. The helium working gas flowed in a central capillary tube, engulfing a needle electrode powered by 13.7 MHz radio frequency sinusoidal voltage. The N2 shielding gas flowed in the annular space of a coaxial tube. These gases emerged, in laminar flow, in a 78%N2-21%O2-1%Ar dry air ambient. The characteristics of the APPJ with shielding gas were compared to those of the APPJ without shielding gas. The nitrogen shielding gas hindered the diffusion of oxygen and argon from the ambient air into the helium jet. With the shielding gas present, more nitrogen penetrated into the helium core, causing a shorter plasma ‘plume’. The flow rates of the working and shielding gas, critically affected the gas temperature, and in turn the discharge characteristics. For a He flow of 2 standard liters per minute (slm), switching on the nitrogen shielding gas flow (at 4.5 slm) reduced the on-axis O2 and Ar mole fractions from to and from to , respectively, at an axial distance of 3 mm downstream of the nozzle. The radial profiles of the mole fractions of the ambient gases were monotonically and strongly decreasing towards the system axis, for short axial distances from the nozzle (∼1 mm), but became progressively flatter at longer distances from the nozzle (3 mm and 5 mm). Simulation predictions captured the salient features of experimental data of ambient species mole fractions in the plasma jet, and the 706 nm optical emission intensity profiles of the He 33S excited state.

Experimental and numerical analyses of parameter optimization of photovoltaic cooling system

When the temperature of photovoltaic (PV) increases, the power generation efficiency decreases almost linearly. The temperature effect caused by high temperature has become an important factor that hinders the production of PV. In this study, the structural layout and the parameter optimization of PV cooling system are conducted. For this purpose, a thermal-electric coupled model of PV cooling system has been set up. Using the mathematical model, the effects of various parameters, such as the type of tube, tube diameter, tube spacing, water inlet temperature and flow velocity are analyzed. The results show that the average surface temperature of PV decreases with the increase of tube diameter and flow velocity and the decrease of tube spacing and water inlet temperature. Furthermore, theoretical parametric values for the optimized configuration of the PV cooling system are obtained. The experimental results show that the optimized PV cooling system can effectively reduce the surface temperature, which is about 47.0 °C lower than that of the non-cooled system. Moreover, the conversion efficiency and the exergy efficiency are exponentially related to mass flow. When the mass flow rate is 0.04 kg/s, the conversion and exergy efficiencies achieved the maximum values of 11.9% and 12.4%. When the water inlet temperature is 10 °C, the conversion and exergy efficiencies achieved the maximum values of 11.6% and 11.7%, respectively. Finally, the economic calculations were carried out in three typical cities in China. The results show that the PV cooling system can increase power generation by 7%–15%.

Dynamic CFD modeling evaluation of ash deposition behavior and morphology evolution with different tube arrangements

A comprehensive CFD model is presented to investigate the deposition behaviors of ash particles with high AAEM contents. The ash deposition behaviors of deposited particles are described via the melt fraction sticking model, the critical impact velocity model coupled with the elastic–plastic deformation theory, and the critical wall shear velocity model. The morphology evolution of ash deposits is predicted by the dynamic mesh method. The effects of longitudinal tube spacing, transverse tube spacing and tube geometry are studied. The oscillatory turbulent vortices, ash particle kinetic energy, and tube arrangement have a combined effect on the fates of impacting ash particles. A large S1/D has the tendency to enhance the accumulation of ash deposits on the rear rows of tube bundles. The peak of the ash deposits on the windward side is higher at a small S2/D. Elliptical tube bundles are practically promising and feasible applications due to the reduction of vortex shedding and the alleviation of ash deposit formation.

Assessment of different techniques for the administration of inhaled salbutamol in children breathing spontaneously via tracheal tubes, supraglottic airway devices, and tracheostomies.

Perioperative respiratory adverse events account for a third of all perioperative cardiac arrests, with bronchospasm and laryngospasm being most common. Standard treatment for bronchospasm is administration of inhaled salbutamol, via pressurized metered dose inhaler. There is little evidence on the best method of attaching the pressurized metered dose inhaler to the artificial airway during general anesthesia. The aim of this study is to investigate the best method to deliver aerosolized salbutamol via pressurized metered dose inhaler to the lungs of an anesthetized child. We measured salbutamol delivered by pressurized metered dose inhaler through different sized tracheal tubes, supraglottic airway devices, and tracheostomies in vitro for methods commonly employed for connecting the pressurized metered dose inhaler to the artificial airway. Breathing was simulated for patients weighing 3, 16, 50, and 75kg. Pressurized metered dose inhaler actuation coincided with inspiration. A pressurized metered dose inhaler combined with an in-line non-valved or valved spacer, or the direct method, when delivered via tracheal tube, was linked with improved delivered dose of salbutamol, compared to all other methods for 3 or 50kg simulated patients weights. The delivered dose when using a non-valved spacer was greater than all methods for 16 and 75kg patient weights. A spacer improved delivery for the flexible supraglottic airway device type, and there was no difference with or without a spacer for remaining types. Via tracheal tube and non-valved spacer, the following doses should be delivered after single actuation of a 100µg labeled-claim salbutamol dose: ~2µgkg-1 per actuation to a 3kg neonate, ~1µgkg-1 per actuation to a 16kg child, and~0.5µgkg-1 per actuation for a 50-75kg child. The least effective methods were the syringe, and the uni- and bidirectional adaptor methods, which require replacement by the direct method if a spacer is unavailable.

Using a sunrays trap in direct-absorption solar collector (DASC) to enhance the thermal efficiency of collector

In this work, a new model of direct absorption solar collector (DASC) is presented, in which for the first time one sunrays trap is applied to capture as much solar energy as possible and consequently to enhance the efficiency of the collector. Also, the second innovation of the presented model is the sequential reflections of sunrays in the receiver tube which leads to the augmentation of sunrays path length and subsequently the reduction of the nanoparticles agglomeration based on Beer-Lambert law. The reduction of nanoparticles agglomeration can decrease the cost and higher operational stability. To achieve the higher efficiency and stability, as well as the reduced cost, the new-presented sunrays trap is comprised with an evacuated envelope surrounding the receiver tube as well as a compound parabolic concentrator (CPC) which swallows the sunrays. The walls of the receiver tube and envelope are reflective and insulated respectively which attenuate the heat losses from receiver tube in which Plasmonic nanofluid is applied to collect solar energy. The COMSOL software is applied to trace sunrays optically and then to simulate the internal space of receiver tube numerically. Using the validated simulation method, the effects of variables on collector efficiency are analyzed. These variables include the width of the CPC exit (w2), the outer diameter of receiver tube (do), absorption coefficient (α), the place of focus point, and inlet temperature (Ti). Finally, it was concluded that using presented collector not only results about 4% more efficiency than the conventional DASC, but also can significantly reduce the agglomeration of nanoparticles in the base fluid. These positive results can be achieved vesus Ti = 310 K, α.P=3.46, and do = 7 cm.

A Simplified Thermal Design Model for a Single Vertical U-Tube Borehole Utilized in Ground-Coupled Source Heat Pumps

The present work dealt with the thermal assessments of the ground-coupled heat pump heat exchangers utilized in the field of geothermal energy source. A model was performed to predict the overall thermal resistance of a single vertical heat exchanger embedded in the borehole. The philosophy of the U-tube replacement with a single equivalent tube size was implemented with new development. Four tube sizes were used to build several borehole geometry configurations, they were (9.53) mm, (12.7) mm, (15.88) mm, and (19.05) mm accommodated in borehole sizes of (65) mm, (75) mm, (90) mm, and (100) mm respectively. Twelve borehole geometry configurations were examined as DX condensers circulate R410A refrigerant. These geometry assemblies produced a range of (0.29-0.57) for tube spacing to borehole ratio tested at (0.73) W/m K to (1.9) W/m K filling thermal conductivity range. The results of the present correlation showed good agreement with previously published correlations in the open literature. A mean temperature difference between the condensed vapor refrigerant and soil was assumed to have existed as (14) °C. Increasing the tube spacing from (2) to (3) times the tube diameter exhibited an augmentation in the heat loading of the borehole. This rise in the heat loadings of the U-tube was (8-10) % and (13-17) % for the geometry configurations of (9.53) mm and (12.7) mm tube sizes respectively. The tube diameter has also shown its importance in the thermal process of the borehole. At (75) mm borehole size and tube spacing of (2) times tube outside diameter, the predicted borehole thermal resistance for (9.53) mm tube diameter was higher than that of (19.05) mm one by (78-80) % for the test range of grout thermal conductivity.

Study on Flow Interference of Multi-group Parallel Jets between Heat Transfer Tubes

In order to find an approach to optimize the hydraulic cleaning equipment of steam generator secondary side of CPR1000 reactor, the Computational Fluid Dynamics (CFD) method was used to simulate the flow of multiple groups of parallel jets. In this simulation, the RNG k-ε turbulence model and the gas-liquid two-phase flow model is employed to distribute the jet flow between heat transfer tubes. The results show that with the increase of the jet angle, the pressure aggregation on the tube sheet decreases obviously, which is caused by the deflection force due to the pressure difference between the two sides of the jet. With the jets distance increasing, the interaction between jets decreases obviously. When the distance is up to more than nine times of tube spacing, the force that causes deflection of the jet will almost disappear. With this distance, the jets can maintain a good linearity and obtain a satisfied cleaning effect on the heat transfer tubes.

Spray and mixing characteristics of liquid jet in a tubular gas–liquid atomization mixer

For the design and optimization of a tubular gas–liquid atomization mixer, the atomization and mixing characteristics of liquid jet breakup in the limited tube space is a key problem. In this study, the primary breakup process of liquid jet column was analyzed by high-speed camera, then the droplet size and velocity distribution of atomized droplets were measured by Phase-Doppler anemometry (PDA). The hydrodynamic characteristics of gas flow in tubular gas–liquid atomization mixer were analyzed by computational fluid dynamics (CFD) numerical simulation. The results indicate that the liquid flow rate has little effect on the atomization droplet size and atomization pressure drop, and the gas flow rate is the main influence parameter. Under all experimental gas flow conditions, the liquid jet column undergoes a primary breakup process, forming larger liquid blocks and droplets. When the gas flow rate ( Q g ) is less than 127 m 3 ·h −1 , the secondary breakup of large liquid blocks and droplets does not occur in venturi throat region. The Sauter mean diameter (SMD) of droplets measured at the outlet is more than 140 μm, and the distribution is uneven. When Q g > 127 m 3 ·h −1 , the large liquid blocks and droplets have secondary breakup process at the throat region. The SMD of droplets measured at the outlet is less than 140 μm, and the distribution is uniform. When 127 < Q g < 162 m 3 ·h −1 , the secondary breakup mode of droplets is bag breakup or pouch breakup. When 181 < Q g < 216 m 3 ·h −1 , the secondary breakup mode of droplets is shear breakup or catastrophic breakup. In order to ensure efficient atomization and mixing, the throat gas velocity of the tubular atomization mixer should be designed to be about 51 m·s −1 under the lowest operating flow rate. The pressure drop of the tubular atomization mixer increases linearly with the square of gas velocity, and the resistance coefficient is about 2.55 in single-phase flow condition and 2.73 in gas–liquid atomization condition. The breakup morphologies of liquid jet with different liquid and gas flow rates are photographed by a high-speed camera respectively. The liquid jet column swings and breaks up into large droplets and liquid blocks in the air flow. When flow through the Venturi throat, these large droplets and liquid blocks break up into smaller droplets. The particle size and velocity distribution of atomized droplets were measured by Phase-Doppler anemometry (PDA). Under the same gas flow rate condition, the droplet sizes at different measured points are basically the same, and the droplet size decreases gradually with the increase of gas velocity. With the increase of gas velocity, the droplet size distribution of each measured point is closer to a straight line, and the uniformity of atomized droplet distribution in the tube is better. With the value of the gas velocity 72 m 3 ·h −1 , the average droplet size is about 200 μm, and with the value of the gas velocity 216 m 3 ·h −1 , the average droplet size is about 50 μm. • Experiments were performed on droplet size and velocity in tubular atomizing mixer. • Breakup morphologies of liquid jet under different flow conditions were obtained. • The relationship between gas flow rate and droplet size was obtained. • Gas–liquid atomizing and mixing characteristics in tubular mixer were analyzed.

Molecular simulation study on the radon adsorption behavior in carbon nanotube bundles

As we know radon is harmful to people because of its radioactivity. Focusing on the technical requirements of radon mitigation by adsorption, the radon adsorption behavior of carbon nanotube bundles was studied under different diameter tube bundles and different tube spacing using the grand cononical ensemble Monte Carlo (GCMC) simulation method. The results show that the (10:10) type nanotubes have the strongest ability to adsorb radon with a tube spacing of 1 nm, followed by (7:7) type nanotubes with a tube spacing of 1 nm. The bundle of carbon nanotubes of the (8:8) type has the worst adsorption capacity. Moreover, the nanotube bundles of each type of tube have an increased ability to adsorb radon as the tube spacing increases.

Optimization of a solar water heating system for vapor absorption refrigeration system

AbstractIn this work, the optimization study of the solar collector integrated, with a thermal energy storage tank for the vapor absorption refrigeration system, was studied using TRNSYS. The performance of the integrated system was evaluated considering major contributing parameters such as solar collector area, the mass flow rate of the operating fluids, storage tank volume and height, absorber plate thickness, tube spacing, absorber tube diameter, insulation thickness, and glass thickness/properties, respectively. A physical model of the complete solar water heating (SWH) and refrigeration system was developed followed by simulation studies of the major components for optimization, and finally, the obtained results were compared with the reported data for validation. The results indicated that, by using the solar power with a serpentine tube type flat plate collector of area 24 m2 and a storage volume to a specific collector area of about 60 Lm−2, the optimized system could meet 65% of the annual thermal energy requirement for the refrigeration unit. Further, the annual performance of the optimized solar collector in terms of collector efficiency, heat removal factor, and overall heat loss coefficient was found to be about 0.32, 0.87, and 2.99 W m−2 K, respectively. In addition, the optimization approach that is adopted using TRNSYS in the present study could be used for optimizing the solar‐based energy system for various applications.

Effects of alternate moistube-irrigation on soil water infiltration

Alternate moistube-irrigation is a new type of water-saving irrigation, and research on water infiltration with alternate moistube-irrigation is important for the design of irrigation schemes and helpful to understand and apply this technology. The effects of the pressure head (1.0 m and 1.5 m) and tube spacing (10 cm, 20 cm, and 30 cm between two moistubes respectively) on soil water infiltration in alternate moistube-irrigation were studied in laboratory experiments, and the cumulative infiltration, discharge of the moistube, and shape and water distribution of the cross-section of the wetting front were determined. The cumulative infiltration increased quickly and linearly with the infiltration time at 0-96 h (R2>0.99), and changed smoothly at 96-192 h with a basically steady infiltration rate. The discharge of the moistube increased rapidly at the beginning of irrigation, then decreased before stabilizing. The cumulative infiltrations and discharges of moistube under the 1.5 m pressure head were more than those under the 1.0 m pressure head. The shape of the cross-section of the wetting front for a single moistube was similar to a concentric circle. With the increase of tube spacing, the interaction between water infiltrations of two moistubes decreased. The soil water distributions around two moistubes were similar to each other under the 1.0 m pressure head and large tube spacing. When the tube spacing was 20 cm, the soil water distribution was more uniform around two moistubes. Keywords: alternate irrigation, moistube-irrigation, soil water infiltration, water use efficiency, water-saving irrigation DOI: 10.25165/j.ijabe.20201304.5297 Citation: Shen L X, Zhang Y M, Yang M, Liu R H. Effects of alternate moistube-irrigation on soil water infiltration. Int J Agric & Biol Eng, 2020; 13(4): 151–158.

Photovoltaic thermal collector assisted heat pumps using environment-friendly working fluids

In this research, a photovoltaic-thermal collector assisted heat pump has been developed and tested its performance under the tropical climatic conditions of Malaysia. The refrigerants such as, R134a and R1234yf were selected based on its thermodynamic and thermo-physical properties. The temperature of the photovoltaic module was theoretically predicted under the influence of tube diameter, tube spacing and refrigerant mass flow rate. Further, the energy performance of the photovoltaic-thermal evaporator and the heat pump system are investigated experimentally. Finally, the economical feasibility of the photovoltaic-thermal collector evaporator was assessed for the period of 20 years. The results showed that, the tube spacing and diameter of the copper tubes used in the photovoltaic-thermal evaporator/collector using R134a and R1234yf were optimized to 80 mm and 12.7 mm, respectively. It was observed that, during the clear sunny day, the average photovoltaic module temperature was reduced to 30.9 °C under the influence of panel cooling using refrigerant. The output of the panel was enhanced by 21%–44% with increase in solar radiation from 400 W/m2 to 1000 W/m2. The coefficient of performance of the heat pump was varied from 4.8 to 6.84 with an average coefficient of performance of 5.8 during clear sunny days. The life cycle economic analysis indicated that, the photovoltaic-thermal collector evaporator assisted heat pump has a payback period of 3 years, whereas the reference photovoltaic system has a payback period of 8 years.

The effect of geometrical modifications to a shell and tube heat exchanger on performance and freezing risk during LNG regasification

The regasification of LNG is a crucial process in a majority of LNG applications and can be conducted in various types of heat exchangers. The low boiling temperature of LNG makes the vaporization process prone to the risk of ice formation, which can obstruct the flow of the heating fluid. This, in turn, can lead to a significant drop in pressure, decrease in heat transfer or even to the destruction of the heat exchanger itself. In a wide range of important applications, the heating fluid is often water or a water-glycol mixture, characterized by a freezing temperature that is substantially higher than the boiling temperature of LNG. Consequently, this can intensify the ice formation process. In the current research, a numerical model was proposed and developed to analyze the risk of ice formation during the LNG vaporization process within a shell-and-tube type of heat exchanger (STHX). The model consists of two distinct parts: heat transfer through the boiling LNG and the freezing dynamics of the heating fluid. To generalize the developed model for various boiling regimes a continuous and differentiable expression of the boiling curve of LNG was proposed. The expression smoothly connected the nucleate with the film boiling regions and methodically filled the gap of the transition region. The developed numerical model was used to investigate a wide range of flow conditions and various shapes and spacing of tubes within the STHX. It was shown that the risk of total freezing could be indicated by a critical value of the Reynolds number. The conducted study made it possible to define a heat-flux-to-pump-duty-ratio coefficient, which showed that flattened tubes could ensure better heat transfer, higher reliability and also decrease the pump duty needed to supply the STHX.

Performance Analysis of Membrane Separation Process for Water and Heat Recovery from Flue Gas

Membrane separation process can simultaneously recover water vapour and waste heat from flue gases, which has great potential for water and energy savings. Composite ceramic nanoporous membrane is one of the emerging technologies showing the good performance of water vapour and waste heat recovery from the flue gas of power plants. However, the flue gas has great property changes along a flue resulting in a dramatic performance change of membrane separation. Current experimental studies couldn’t provide enough experience to explore the performance of membrane modules in a wide range of working conditions and structure configuration. In this paper, a calculation model is established based on thermodynamic mechanisms of membrane separation process to simulate the performance of ceramic membrane modules under different structure configuration and working conditions. Three cases are conducted to analyse the effects of module configuration and parameter selection in a ceramic membrane module. Results show that a ceramic membrane module placed before the desulphurisation tower can recover more heat, while after the desulphurisation tower it can recover more water. There would be an optimal tube diameter and an optimal tube spacing for water recovery under specific working conditions. These results show great adaptability of the calculation model and could guide the system design of membrane separation modules in water vapour and waste heat recovery.

Experimental study on particle flow characteristics of three-dimensional moving bed

The disorderly treatment of blast furnace slag has caused huge energy waste. To tackle this issue, moving bed are continuously attracting worldwide attention. In this paper, the in-depth analysis of the flow characteristics of blast furnace slag-like particles in a solid-solid heat transfer moving bed is carried out. The particle flow pattern and velocity in the moving bed with different tube numbers, configurations and spacings are vividly recorded. Significantly, a quantitative formula of the mass flow rate including the opening width, the bed layer height, the tube number and spacing, the particle size and distribution was built for this solid-solid heat transfer model. Furthermore, it is found that the longitudinal velocity distribution of the particles renders obvious peaks and valleys along the width direction. This study provides theoretical guidance for the optimization of the structure and operational parameters of the solid-solid heat-exchange moving bed.

Experimental investigation of perforated twisted tapes turbulator on thermal performance in double pipe heat exchangers

In this paper, the experimental effect of the continuous and discontinuous twisted tapes turbulator (perforated and non-perforated) on the inner side of the internal tube in the double heat exchangers on heat transfer, the friction coefficient, and thermal performance have been discussed. On discontinuous twisted tapes turbulator, 9 holes with different geometries, such as triangular, square, rectangular, circular, and diamond with the triangular arrangement, have been created on turbulator flat surfaces. The Reynolds range is investigated at 5500–10000, and working fluids are on the side of the inner tube and annular space is hot and cold water, respectively. Experimental results have shown that discontinuous turbulator has a better effect on heat transfer and pressure drop than continuous turbulator. As the discontinuous turbulator without a hole has an increase in heat transfer of 8.2 % and a reduction of 9.8 % in the pressure drop coefficient compared to the continuous turbulator. Then the effect of perforation on discontinuous twisted tapes turbulator was investigated. Experimental results show that perforated discontinuous turbulator with circular, square, rectangular, diamond and triangular perforation with the same hydraulic diameter as for discontinuous turbulator without perforation was 20.8 %, 15 %, 11 %, 8.7 %, 5 % increase in heat transfer and 27.7 %, 22.8 %, 17.3 %, 12.1 %, 5.5 % decrease in the coefficient of pressure drop, respectively. Therefore, according to the results, the best thermal performance was related to the perforated of perforated discontinuous twisted turbulator, discontinuous twisted turbulator, and continuously twisted turbulator were respectively.