Thermal Performance Parameters Research Articles

Energy and exergy analyses of a coal-fired micro-CHP system coupled engine as a domestic solution

In this study, a coal-fired stoker boiler and a beta-type rhombic-drive Stirling engine were manufactured and tested. The performance of the coal boiler with a Stirling engine has been investigated experimentally for the heating system of a three-storey house. The aims of this study are to investigate the Stirling engine's electricity generation potential and thermal energy production. Also, energy and exergy analyses of the micro-CHP system were performed to evaluate thermodynamic performance. Measurements were taken at 10-min intervals for three months. Thus, the temperature values, thermal power, thermal performance, efficiency, energy rates, exergy rates, and electrical parameters of the micro-CHP system can be monitored. The heating demand of the building was covered totally by the micro-CHP system, and the thermal power of the stoker boiler was reduced by approximately 1.29 kW due to the integration of the Stirling engine. The daily total of 2.6 kWh of electricity was generated with the Stirling engine and stored in the battery, and the rest of the electrical energy demand was taken from the grid. If the heating system is supported by PV, it can be operated off-grid. This study will provide insight into the usage of micro-CHP systems in residential applications.

Transient study of thermal stratification of full-scale chilled water storage tank during optimum discharge condition

Thermal stratification of full-scale Chilled Water Storage Tanks (5855 m3) with 18 m tank diameter, and 23 m water depth during discharge mode and optimum condition was studied. The experimental and numerical analyse of stratified thermal storage tank in full-scale dimension and discharge mode has been studied. A 3D and 2D numerical model was performed. The case simplified to divide into two parts, the first part was to simulate flow in pipes and radial diffuser, and the second part included simulation in the tank according to the part one results. The optimum operation condition which found from many tests of tank operation conditions according to high thermal stratification and low thermal mixing inside the tank. Validation test with experimental data obtained from the present work and literature. The results included to analyse the thermal stratification and the flow characteristics during the discharging mode. Also, thermal performance parameters such as discharge efficiency, Richardson number, stratification efficiency, thermocline thickness, the average temperature in the tank, and discharge temperature were presented. The important result of the above analysis was the optimum stratification phenomena in the tank with low thermal mixing. The contribution of this study was the numerical modelling and simulation setting to capture the experimental results of these phenomena in the full-scale thermal storage tank, moreover to specify the optimum condition of thermal stratification of this tank dimension, diffuser type, and flow rate.

Comparative study of V-ribs miniature with dimple hybrid roughness along with dimples shaped roughness used in solar air heating system

ABSTRACT In this work, a numerical and experimental study on flow-dynamics and heat transfer in a solar air heater (SAH) provided with dimpled and dimple with v-miniature as roughness element over plate (absorber). For experimental study a staggered dimple was created on the plate (absorber) as a roughness element and ANSYS was used for the simulation. By providing the relative longway length (L/d), relative depth of dimple, and relative short way length (S/d) range from 15–25, 0.024–0.036, and 10–15, respectively. The RNG k-ε model was used to model turbulence, and Nusselt number and friction factor values are estimated for a proposed roughness. The simple duct was validated using Dittus Boelter along with this comparison is also made for roughened plate with experimental and numerical values. The thermal and hydraulic performance parameter of the proposed roughness was also studied by varying the Reynolds numbers from 5000 to 20,000. Results revealed that dimple with v-miniature at relative short way lengths (S/d) value of 15 shows the highest heat transfer at Reynolds number value of 20,000. It was observed that maximum thermal and hydraulic performance parameter has achieved value of 1.73 at α = 45°, L/d = 20 and S/d = 15 at Reynolds number 20,000 for the dimple with v-miniatures roughness.

Thermal and hydraulic characteristics of an air heater with modified delta flow obstructions

Air heaters are extensively used for various applications like space heating, drying of agricultural products etc. Air heaters are low efficient due to poor heat transfer properties of air. Flow obstructions enhances the heat transfer coefficient of air by disturbing the formation of the laminar sub-layer. In this work, the effect of a modified inclined delta obstruction (inclined in the direction of flow (α) and in the direction perpendicular to flow (β) on the thermal and hydraulic performance parameters of an air heater (Nusselt number-Nu, friction factor-f and Thermal Enhancement Factor-TEF). In this study initially, performance parameters of a smooth air heater (size: 30 mm × 50 mm × 300 mm, constant heat flux: 800 W/m2) are analysed using Computational Fluid Dynamics (CFD) at different air flow rates (Re = 5000,10,000,15,000 and 20,000). In the second stage, experiments are conducted on a bench-scale setup using the same conditions to validate the results obtained from CFD. Results from the CFD study were also validated by using empirical correlations (Dittus – Boelter equation and Modified Blasius equation). In third stage, the effect of orientation (α: orientation in the direction of flow, β: orientation in the direction perpendicular to flow) of the modified delta flow obstructions was studied using CFD. From the present study, it is observed that the thermo-hydraulic performance of modified delta obstruction is found to be superior to conventional delta flow obstructions. Modified delta obstructions enhance Nu by 4 to 6 times and increase pressure drop by 6 to 10 times in comparison to the air heater without obstruction. From the numerical study, it was observed that the modified delta flow obstruction improves the performance of the air heater in comparison with conventional delta obstruction and the maximum TEF of 1.99 was obtained at Re =5000, α = 300 and β = -450.

EFFECTS OF NANOREFRIGERANTS FOR REFRIGERATION SYSTEM: A REVIEW

In this article various nanorefrigerants have been critically reviewed towards the performance enhancement of the refrigeration system. Research has been more focused on the different techniques to prepare nanorefrigerants. This paper is an attempt to summarize all aspects of nanorefrigerants such as preparation, thermophysical properties, hydrodynamic study, boiling heat transfer, and performance of nanorefrigerants. It also discusses the effects of different nanoparticles on thermophysical properties. Nanorefrigerants are a special category of nanofluid, advanced nanotechnology-based refrigerants that are stable mixtures of nanoparticles and base fluid, which improve thermophysical properties such as heat transfer and pressure drop and bring compactness to the system. This article presents an overview of improving thermal performance by using different nanoparticle blends with different base refrigerants. Further, influential parameters of nanoparticles and thermal performance are discussed. This paper also discusses the effects of different nanoparticles such as Al<sub>2</sub>O<sub>3</sub>, TiO<sub>2</sub>, CuO, carbon nanotubes (CNTs), etc., on thermophysical properties. The present situation requires a robust system and refrigerants for required performance. Some refrigerants cannot be used directly. So, this paper deals with using nanorefrigerants for better system performance such as coefficient of performance (COP) enhancement, compressor work reduction, and energy efficiency. It is seen that the use of nanorefrigerants, or nanotechnology-based refrigerants, results in highly effective cooling and thus enhances the thermophysical properties of refrigeration systems.

Emitting Electrodes Effect on the Enhancement of Heat Transfer by a Two Stage Electrohydrodynamic Gas Pump

In this study, emitting electrodes effect on the enhancement of heat transfer by a two stage electrohydrodynamic (EHD) gas pump is numerically analyzed. This study is implemented for a two stage EHD gas pump with 24 emitting electrodes configuration and the results are compared with 8 and 56 emitting electrodes configurations. The EHD gas pump is evaluated for a wide range of operating voltages starting from 20 kV up to 28 kV and wide range of Reynolds numbers (Re). The Reynolds numbers considered in this study varies in a range between 100 and 2000. At Re = 100, a maximum increase of 42% in the average Nusselt number is achieved with an applied voltage of 28 kV. The overall effectiveness of the EHD gas pump in heat transfer enhancement is evaluated by the thermal hydraulic performance parameter, (Nu/Nu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> )/(f/f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ), which is always greater than unity. EHD technique has a great potential.

Fault location in a marine low speed two stroke diesel engine using the characteristic curves method

&lt;abstract&gt;&lt;p&gt;When a malfunction occurs in a marine main engine system, the impact of the anomaly will propagate through the system, affecting the performance of all relevant components in the system. The phenomenon of fault propagation in the system caused by induced factors can interfere with fault localization, making the latter a difficult task to solve. This paper aims at showing how the "characteristic curves method" is able to properly locate malfunctions also when more malfunctions appear simultaneously. To this end, starting from the working principle of each component of a real marine diesel engine system, comprehensive and reasonable thermal performance parameters are chosen to describe their characteristic curves and include them in a one-dimensional thermodynamic model. In particular, the model of a low-speed two stroke MAN 6S50 MC-C8.1 diesel engine is built using the AVL Boost software and obtaining errors lower than 5% between simulated values and test bench data. The behavior of the engine is simulated considering eight multi-fault concomitant phenomena. On this basis, the fault diagnosis method proposed in this paper is verified. The results show that this diagnosis method can effectively isolate the fault propagation phenomenon in the system and quantify the additional irreversibility caused by the Induced factors. The fault diagnosis index proposed in this paper can quickly locate the abnormal components.&lt;/p&gt;&lt;/abstract&gt;

Evaluation of thermal performance factor by hybrid nanofluid and twisted tape inserts in heat exchanger

The thermal performance parameters of an improved heat exchanger tube fitted with various vortex generator inserts were investigated using numerical and experimental methods. The governing equations have been solved numerically by a Finite Volume approach employing the turbulence model (κ−ε). Two twisted tape types, which being inserted across a circular pipe (plain twisted tape) and (Double V-cut twisted tape), have been achieved. The hybrid nanofluid is prepared by using metal oxide [Al2O3+CuO] with distilled water at volume fraction range (0.6%, 1.2% and 1.8%), Reynolds number range (3560–8320) at twisted ratio (9.25). The experimental data for a plain tube, plain twisted tapes and double v-cut twisted tape are validated using the standard correlations available in the literature. The effect of such variables upon the average Nusselt number, friction factor, and thermal performance factor have been investigated and compared with a plain tube at the same conditions. As compared to plain twisted tape, the tube equipped with a double V-cut twisted tape with hybrid nanofluid displayed increased thermal performance. The greater vortex flow induced by the V-cuts results in more active thermal boundary layer disturbance, resulting in a greater heat transfer rate. The results show that thermal performance factor for hybrid nanofluid in plain circular tube at (∅=1.8%) and Reynolds number (8320) is about (1.068), when the plain twisted tape and double v-cut twisted tape inserted with hybrid nanofluid the thermal performance factor increased to (1.33) and (1.37), respectively. The results show a similar trend for both numerical and experimental cases. The comparison between the experimental and numerical results have maximum error was (9.7)%.

Experimental Energetic and Exergetic Performance of a Combined Solar Cooking and Thermal Energy Storage System

Most solar cookers usually perform a single task of solely cooking food during sunshine hours. Solar cookers coupled with thermal energy storage (TES) material for off-sunshine cooking are usually expensive and require complex engineering designs, and cannot be used for dual purposes, for example, solar water heating and cooking. In this paper, a solar cooker that can perform dual tasks of cooking as well as storing thermal energy to be used during off-sunshine periods is presented. The experimental setup is composed of a parabolic dish, a solar receiver coupled with a flat plate and an oil-circulating copper coil for charging and discharging a storage tank. The objective of the experiment is to evaluate the energy and exergy thermal performance parameters of the dual-purpose system during charging and discharging cycles. The effect of the flow rate and the mass of the load are investigated while using sunflower oil as both the heat transfer fluid and the storage material. Charging and discharging experiments are conducted using four different flow rates (2, 3, 4, 5 mL/s), and with different masses (0.5, 1, 1.5, 2.0 kg) with water and sunflower oil as the test loads. The charging results show that the average energy and exergy rates as well as their corresponding efficiencies increase with an increase in the charging flow rate. On the other hand, the increase in the mass load tends to decrease marginally the average charging energy and exergy rates for water, and their corresponding efficiencies. For sunflower oil, the average charging energy and exergy rates and efficiencies showed a more pronounced decrease with an increase in the mass. Water generally shows higher charging and discharging energy and exergy efficiencies compared to sunflower oil with an increase in the flow rate. For discharging results, the correlations between the energy and exergy thermal performance parameters with respect to the flow rate and the heating load are not well defined possibly due to different initial storage tank temperatures at the onset of discharging and the inefficient discharging process which needs to be optimized in future.

Investigation of fluid flow and heat transfer in a narrow channel with micro barchan-dune-shaped humps

• A bionic heat sink with micro barchan-dune-shaped humps is proposed. • The micro dune can reinitialize the boundary layer by inducing a secondary flow. • The micro dune generally outperforms traditional fins in overall heat transfer performance. This paper proposes an innovative bionic heat sink with micro barchan-dune-shaped humps for improving the flow and heat transfer performance of the smooth narrow channel. The effects of the Reynolds number of the main flow ( Re ) and pitch distance of the dune array ( P ) on the thermal-hydraulic performance are investigated. In this work, the air is the working flow. The Reynolds number range is considered to cover the regimes of laminar, transitional, and turbulent, Re = 860–6,050, and the pitch distance ( P ) equals 8, 12, and 16 mm. The results show that the micro barchan-dune-shaped hump can induce a secondary flow downstream of the slip face and enhance the local heat transfer performance. For the multi-dune models, the case with P = 16 mm provides the highest overall thermal performance parameter ( η ). The η value decreases monotonically with decreasing P in the considered range. In addition, compared with other micro pin fin shapes (including the hexagonal cylinder, square cylinder, and triangular cylinder), the η of the barchan dune shape is almost identical to that of the hexagonal cylinder and exceeds the other two shapes by more than 20%.

Design and Analysis for Heat Transfer Through Twisted Tape with Nanoparticles

Different techniques have been used to achieve a high heat transfer rate. Among them, one of the advanced techniques is a suspension of nanoparticles in the base fluids as water and coated with aluminum and titanium. The present work has been carried out on a double pipe heat exchanger with twisted tape insert with twist ratio (y/w = 4 and 6) and thickness (0.8mm) for heat transfer investigation of water to water and nanofluid to water with counter flow arrangement under turbulent flow conditions. The computational fluid dynamic code simulates different concentrations of nanofluid (0.01% to 0.19%) in ANSYS FLUENT R 18.1 software. The overall heat transfer coefficients for all concentrations are measured as a function of the hot and cold stream's mass flow rates. The thermal performance parameter overall heat transfer coefficient is compared for nanofluids with water. The work concludes that there is a good enhancement in heat transfer rate using nanofluid.

Experimental analysis of the thermal energy storage potential of a phase change material embedded in additively manufactured lattice structures

Recent literature introduced novel additively manufactured porous metallic structures designed to deliver enhancement of the thermal conductivity of organic phase change materials. Among these, so-called lattice structures are of particular interest for application in lightweight components. Originally investigated for their attractive mass-specific mechanical properties, these geometries were recently proposed, in alternative to metallic foams, as a conductive matrix of phase change materials. However, the geometrical parameters of a lattice structure differ from the ones of a metallic foam and no established data exist in the literature about the influence of the lattice cell geometry on the transient heat transfer enhancement of a phase change material. This work presents an experimental comparison of the thermal behaviour of a composite based on an n-Octadecane paraffin wax embedded in four different aluminium lattices with varying unit cell topology (f2ccz, bcc, bccz, f2bcc), but showing the same cell size, aspect ratio and strut diameter. It is noticed that the unit cell topology affects the transient thermal behaviour beyond its direct effect on the cell porosity. To address this, a specific thermal performance parameter is identified. The sample based on the f2ccz topology represents the best candidate. The influence of orientation with respect to gravity on the heat transfer is also investigated. While the samples show relatively low porosity, ranging from 70.7% to 83.4%, the wide pore diameters lead to a high impact of melt convection on the thermal behaviour of most samples. Up to 28% wall temperature variation is evidenced for different heating orientations.

Numerical investigation of pulsating flow structures and heat transfer enhancement performance in spherical corrugated helical tube

• Pulsating flow benefits heat transfer of helical tube with spherical corrugation. • Flow field and local heat transfer characteristic of a pulsating cycle are analyzed. • Optimum dimensionless pulsating frequency for thermal performance is Wo = 35. • Overall thermal performance parameter TP is in the range of 1.06–1.13. In this study, the innovative technology of a square wave pulsating flow combining with a spherical corrugated wall structure was applied in a helical tube to enhance heat transfer. Subsequently, the unsteady flow structure and heat transfer characteristics were numerically investigated. The accuracy of the numerical results was verified using experimental data and results in the open literature. For constant values of the geometrical parameters of the spherical corrugated helical tube, the effects of pulsating parameters on the heat transfer enhancement performance were explored, including dimensionless frequency ( Wo ) and dimensionless amplitude ( A ¯ ). The results indicated that the disturbance induced by the pulsating flow improved the local flow field inside the spherical corrugation. In addition, the intensity of the secondary flow and the turbulent kinetic energy of mainstream were simultaneously enhanced. Further, during more than 60% of one pulsation period, the average Nusselt number ( Nu m ) was noticeably greater than that in steady flow with the same average velocity. The maximum value of Nu m occurred at the end of the first half cycle and was increased by 38.5%. The optimum dimensionless pulsation frequency was Wo = 35 within the studied range. The Nusselt number and the friction factor increased with increase in the dimensionless amplitude. However, the comprehensive heat transfer enhancement performance was better under smaller A ¯ value. Furthermore, within the scope of the Dean number ( De ) De = 2936–4894, the overall thermal performance ( TP ) parameter was in the range of 1.06–1.13.

Computational study to predict the thermal performance and optimal design parameters of a T-shaped fin subjected to natural convection

The present paper aims to predict the optimal design parameters of a T-shaped fin subjected to natural convection using constructal theory. Both analytical and computational investigations are performed to determine its thermal performance for a wide range of thermo-physical and geometric parameters. Power law type temperature-dependent heat transfer coefficient is assumed for natural convection. For analytical solution Adomian decomposition method is adopted to evaluate the temperature distribution in both the stem and flange part of the fin. A numerical scheme called finite difference method is implemented to validate the analytical results. The temperature distribution obtained from the computational analysis using ANSYS FLUENT 14.0 is lower than that obtained from the analytical calculations. Moreover, the actual heat transfer rate is also compared between the two methods which reveal that the computational analysis gives higher value as compared to the analytical results. Further, optimization study has also been carried out in a generalized way so that either the fin volume or the heat transfer rate can be taken as a constraint. It is found that with the increase in length ratio, the optimum effectiveness is obtained at a higher value of aspect ratio whereas the optimum efficiency is obtained at a lower value of it. Though, a decrease in thickness ratio predicts a higher value of actual dimensionless heat transfer rate.

Experimental Investigation of Thermal Performance Parameters of Drying Air Unit with a Different Flowrate of Liquid Desiccant Solution

Liquid desiccant air-conditioning systems remove directly the latent load from moist air and remove indirectly sensible load of this air by using an indirect evaporative cooling process. The liquid desiccant must subsequently be regeneration once again with a low-grade heat source like solar energy. In this study, calcium chloride solution was used as a desiccant. For the desiccant solution regeneration process, a flat plate solar collector was employed. Different variables, such as the primary airflow rate and desiccant flow rate, were changed during the experiments. The impact of these variables on the performance parameters of the desiccant systems such as moisture removal rate, moisture efficiency, enthalpy efficiency, sensible heat ratio, and the mass transfer coefficient was studied. The obtained results revealed that as the flow rate of primary air increases, the moisture removal rate, sensible heat ratio, and the mass transfer coefficient increase. For example, from 0.006 m/s to 0.0125m/s when the mass airflow rate increased from 0.1 kg/s to 0.18 kg/s.

Concentrating solar cookers in urban areas: Establishing usefulness through realistic intermediate temperature rating and grading

Concentrating Solar Cookers (CSCs) are well-known for fast cooking and can significantly contribute to attaining the United Nation’s sustainable development goals. CSCs attain intermediate temperatures (120–240 °C) and are suitable for several cooking applications. The realistic rating and grading of CSCs is inevitable for establishing their usefulness in urban areas, which is the main objective of the present work. This paper reveals the experimental results of two existing concentrating solar cookers with different geometries and aperture areas. The first cooker is a shallow satellite antenna parabolic dish, and the other is a small deep parabola. Cooker Opto-thermal Ratio (COR) acts as a thermal performance parameter, and glycerin as a test load for their performance evaluation.The mean values of COR for the cookers, CSC1, and CSC3, are 0.180 and 0.092, respectively. The typical theoretical values of maximum achievable fluid temperature are 192.9 and 113.9 °C, respectively, and that for reference time are 23.8 and 60.5 min for CSC1 and CSC3, respectively. COR identifies the variation in the performance of CSCs based on a design change. The objective parameters enable realistic intra-cooker performance comparison of the CSCs at intermediate temperatures. The results depict that the existing designs of CSCs can be graded appropriately using COR and provide new insights into their performance at intermediate temperatures realistically. TPP-based realistic rating and grading of existing designs of solar cookers enable their effortless selection as per end-user requirements and help in the faster propagation of solar cooking technology in urban and semi-urban areas.

Study on the influence of thermo-physical parameters of phase change material panel on the indoor thermal environment of passive solar buildings in Tibet

In this study, an unsteady heat transport numerical model of phase change material (PCM) panel under indoor-outdoor dual thermal disturbance conditions was development by using the apparent heat capacity method, which was employed to evaluate the effect of thermal performance parameters of PCM on the heat storage and temperature regulation capability of PCM panel. Then, a single-space passive solar building located in Tibet was used as a basic building model to study the influence of thermo-physical parameters, such as phase change temperature, thickness and position of PCM panel in composite wall on indoor thermal environment. Meanwhile, the indoor discomfort degree hours and heating energy consumption of the passive solar building with composite wall containing PCM panel were quantitatively analyzed, and the dynamic payback period of PCM investment in Tibet was calculated for economic analysis. The results indicated that the phase transition temperature, thickness and position of PCM panel have a significant impact on its heat storage and temperature regulation capability, and the composite wall containing PCM panel with reasonable thermo-physical parameters could obviously damp indoor air temperature fluctuation and save the building heating energy consumption. Compared with the basic building, applying a 30 mm thickness PCM panel with phase transition temperature of 18 °C on the interior side of the composite wall could reduce indoor discomfort degree hours in studied period (Dec. 20 to Dec. 24) by 74.9% and reduce heating energy consumption in the whole heating period (Dec. 01 to Mar. 01) by 20.76%, respectively. Furthermore, the economic analysis results show that the application of PCM panels in passive solar buildings in Tibet has high economic value, and the dynamic payback period of PCM investment in Tibet with 3% discount rate is 41.29 years, which is lower than the usual service life of a building.

Enhancing forced-convection heat transfer of a channel surface with piezo-fans

The beam shape of a piezo-fan and the inlet turbulence intensity (TI) of channel flow are important parameters that affect the heat transfer enhancement of a heated surface in an airflow channel with a vibrating piezo-fan. In this study, 3D numerical channel models of different piezo-fans are considered when investigating the influence of beam shapes and inlet turbulence intensity on the heat transfer performance of channel flow, within a range of 4000–30,000 Reynolds numbers (ReCF) and 5% to 20% inlet turbulent intensity (TI). The influence of these parameters is analyzed in terms of the distributions of the flow field, time-averaged heat transfer coefficient, and overall thermal performance. The results show that the piezo-fans with the widest rectangular shape and a convergent shape behave better in terms of overall thermal performance in the channel. However, as the turbulence intensity increases to 20%, the difference in heat transfer caused by the beam shape becomes negligible. The maximum overall thermal performance parameter (η) = 1.47 is obtained at ReCF = 13,000 and TI=20% for the convergent beam shape (Beam-E).

A comparative numerical study of shell and multi-tube heat exchanger performance with different baffles configurations

This study presents a numerical modeling of a shell and tube heat exchanger to analyze six various baffle configurations for increasing the thermal parameters performance and hydraulic parameters performance. The baffle configurations include conventional single segmental (CSS), staggered single segmental (SSS), Flower segmental (FS), hybrid segmental (HS), circular ring baffle (CR), and circular ring with holes (CRH) baffles. Flow of water field characteristics, pressure loss, and heat transfer performance, including effectiveness (ε) and the heat transfer coefficient (h) are studied with a variation of Reloads numbers from 10500 to 38500 to analyze the best performance. The effectiveness and the heat transfer coefficient increase with increasing the Reynolds numbers. The HS configuration results are the largest shell side pressure loss while HS and CR thermal influence on heat exchanger performance augmentation is found to be more significant compared to other configurations for all test cases. Compared to the CSS and SSS baffle configurations, the dead spaces and the recirculation zones are disappearing in both FS and HS configurations where the RCH is superior in overcoming the dead zones completely. The maximum values of the effectiveness and heat transfer coefficient of STHX are achieved in the case of CRH type with enhancement about 166% and 142% respectively, compared to CSS baffle. The CRH accomplished less friction losses than hybrid and ring baffles where the shell side pressure drop for HS was the highest value. The heat transfer coefficients per pressure loss of the RCH are about 138% higher than that of other configurations.

Excited state trap in erbium doped borate glass

Erbium doped borate glass is widely used in luminescent materials, the luminescence dynamics of erbium doped borate glass is of great significance for optimizing and improving the luminous efficiency. The 2% molar ratio erbium doped borate glass was synthesized by the traditional melt quenching method, and annealed at 260 °C below the borate glass transition temperature. The thermal performance parameters of borate glass undoped and doped with Er3+ were measured by differential scanning calorimetry with 10 °C/min. The transient emission spectrum and decay kinetics curves were measured for the luminescence mechanism of erbium doped borate. Er3+ ions have different lifetime when emitted at 556 nm with different excitation wavelengths, the excited state trap may exist in erbium doped borate glass.