Outlet Air Temperature Research Articles

Effect of lithium-ion batteries on heating a residential building using PCM: Changing the horizontal distance between batteries

Plate batteries are widely utilized in electronics and telecommunications. Due to the broad application of these batteries, the cooling of two lithium-ion batteries located in an air duct is examined in this article numerically using COMSOL software. Batteries are surrounded by a phase change material (PCM). This study is performed in 10 min by changing the distance between batteries from 2 to 4 cm. The outlet air can be used to heat a building. The finite element method is employed to solve the equations. The findings show a reduction in temperature and a reduction in the quantity of molten PCM (MOP) with an increase in the distance between the batteries from 2 to 3 cm. But when the distance between the batteries is increased by another 4 cm, their temperatures rise and their volume of MOP increases. The minimum and maximum outlet air temperatures correspond to a distance of 2 cm and 3.5 cm, respectively. Most of the energy that can be extracted from the battery cooling system is related to a distance of 3.5 cm between the batteries.

Performance Analysis of the Multi-Stage Dew-Point Indirect Evaporative Air Cooler

In this study, a multi-stage regenerative-cross-flow dew-point evaporative cooler performance is analyzed and compared to the performance of a regenerative dew-point evaporative cooler. The most beneficial configuration of the proposed exchanger was established on the basis of its geometry and performance analysis using validated numerical models. For specific outlet air parameters, it was found that the multi-stage cooler with a working-to-primary air-flow ratio equal to 0.3 reaches 5.6% lower outlet air temperatures and 10.2% higher cooling capacity when compared to the regenerative unit. The proposed cooler provides lower outlet air temperatures for all average outdoor air parameters in selected locations, for both dry and humid outdoor air parameters (e.g., Denver (USA) and Izmir (Turkey)).

Performance of isobaric adiabatic compressed humid air energy storage system with shared equipment and road-return scheme

• Novel isobaric adiabatic compressed humid-air energy storage system was investigated. • Water spray absorbs compression heat and controls compressed air outlet temperature. • Shared equipment and road-return scheme of energy storage/release system is employed. • Optimal system efficiency occurs at compression outlet parameters of 10 MPa/320 °C. • System efficiency reaches 72.6% and theoretic energy storage density is 17.2 kWh·m −3 . To cope with the inherent problem when intermittent renewable energies of solar and wind are connected to the grid, a novel isobaric adiabatic compressed humid air energy storage system was proposed and investigated. This system adopts a single stage dual-usage compressor-expander with synchronous rotating multi-cylinder to replace two separate multi-stage turbine type machines. The temperature of the compressed air is controlled by water spray before compression. The shared equipment with road-return stratagem of thermal oil energy storage/release system is employed. A hydro-assisted isobaric adiabatic compressed air storage system is formed with an underground cavern such as abandoned coal mine as the lower reservoir and a surface reservoir as the upper reservoir, and the nylon cloth pipe system is arranged in the underground cavern to store compressed air around water. By establishing the thermodynamic model of the system, the influences of the outlet pressure and temperature of compression on the system performance were analyzed determined respectively by the depth of the underground cavern and the working temperature of the thermal oil of the energy storage system. The results show that the round-trip efficiency varies slightly with the compression outlet pressure. Under the conditions of compression outlet parameters of 10 MPa/320 °C and the isentropic efficiencies in compression and expansion are 85%, the round-trip efficiency reaches 66.6% and the theoretical energy storage density is 16.5 kWh·m −3 .

Integrating phase change material in building envelopes combined with the earth-to-air heat exchanger for indoor thermal environment regulation

To utilize the combined effects of earth-to-air heat exchanger (EAHE) and phase change material (PCM) in indoor thermal environment regulation during summer, this study proposes a combination mode, i.e., EAHE–PCM. In this method, EAHE continuously provides cool air to indoor spaces. PCM integrated into building envelopes stores excess cold provided by EAHE at night and transfers it indoors across time. We performed two full-scale comparative experiments (EAHE–PCM combined operation mode and PCM alone operation mode) on typical summer days in hot-summer and cold-winter regions. The results showed that the maximum reduction in the EAHE outlet air temperature and moisture content reached 21.6 °C and 4.55 g/kg, respectively, inducing an average cooling capacity of approximately 1186.5 W. The use of EAHE decreased the time-averaged PCM internal temperature by 6.0 °C in 24 h compared to the PCM alone operation mode, thereby activating the phase change process of PCM between 19:54 and 9:45. Therefore, PCM can store excess cold provided by the EAHE via latent heat and transfer it to indoor air through the melting process, resulting in a 157 min lag in the PCM internal temperature rise. When the ambient air temperature varied between 26.3 and 45.2 °C, the EAHE–PCM combined operation mode decreased the time-averaged indoor air temperature by 6.6 °C compared to the PCM operation alone, which helped maintain the indoor air temperature within the comfort temperature range of 22–28 °C for 73% in 24 h, with a peak temperature of 30.6 °C.

RETRACTED: Study of circular, horizontal and vertical elliptical enclosures filled with phase change material in thermal management of lithium-ion batteries in an air-cooled system

In this paper, the battery cooling is examined by placing a battery cooling system in the airflow path. The cooling system consists of 9 cylindrical battery cells so that a phase change material (PCM) surrounds them. PCM is housed in horizontal and vertical elliptical (ELL) and circular enclosures. The amount of PCM used in enclosures is equal and the effect of enclosure shapes on battery temperature (TBat) and the rate of phase change of PCM is evaluated. COMSOL software is employed to simulate the battery cooling system. The results demonstrate that the use of PCM enclosures with vertical ELL shape causes the highest maximum temperature (Tmax-b) and the average temperature (Tav-b) of battery cells, while horizontal ELL ones produce the lowest Tmax-b and the Tav-b. The maximum amount of liquid PCM at different times corresponds to vertical ELL enclosures and the minimum amount of average volume fraction of PCM is related to horizontal ELL enclosures. Utilizing the enclosures with horizontal ELL shapes creates the minimum outlet air temperature. The circular ones have the maximum outlet air temperature.

Thermal performance analysis of helical ground-air heat exchanger under hot climate: In situ measurement and numerical simulation

The ground air heat exchanger (GAHE) is a promising passive approach for cooling and heating buildings. In this study, thermal performance of helical ground air heat exchanger (HGAHE) has been experimentally assessed in summer season for arid climate. The findings revealed that, the outlet air temperature of the HGAHE is strongly dependent on the inlet air temperature. Furthermore, the air temperature drop and the heat exchange rate as high as 13.3 °C and 463.4 W respectively, are attained at the highest inlet temperature of 41.0 °C. Besides, a transient numerical model was established and validated through the experimental data to investigate the heat penetration into the borehole. The results acknowledge that, the borehole temperature distribution in axial direction is higher at the upper surface and then decreases with the HGAHE length. In the other hand, the borehole temperature distribution in the radial direction reduces rapidly with the distance away from the pipe surface. Moreover, when the ambient air temperature during the night shift is lower than the borehole temperature, the forced convection which helps to take the heat away via purge air circulating into the HGAHE pipe allowed the borehole to restore its cooling ability.

Experimental performance of a three-fluid desiccant contactor using a novel ionic liquid

• Novel Ionic Liquid that is not corrosive to aluminum is used as liquid desiccant. • New three-fluid fin-tube desiccant contactor fabricated using aluminum. • Experimental performance of the fin-tube contactor using IL solution is investigated. • The fin–tube contactor showed superior performance than the packed bed contactor. • Lower solution flow rates and pumping power is expected using the fin–tube contactor. The experimental performance of a new three-fluid fin–tube contactor using a novel ionic liquid desiccant solution is investigated and compared with those of an adiabatic packed bed contactor with LiCl solution for liquid desiccant air conditioning system applications. Owing to the compatibility of the ionic liquid solution with aluminum, a fin–tube contactor is manufactured to exploit internal cooling from a third fluid. The results indicate the superior dehumidification performance of the fin–tube contactor, which yielded an outlet air humidity ratio of 10.5 g w ·kg da -1 at a solution mass flux of 3.06 kg·m −2 ·s −1 , as compared to a similar humidity ratio at a solution mass flux of 4.98 kg·m −2 ·s −1 achieved by the packed bed contactor. In terms of cooling performance, the outlet air temperature of the fin–tube contactor is 21.9 °C, which is lower than that of the packed bed contactor even at its highest solution mass flux. This indicates that the cooling performance of the fin–tube contactor has minimal dependence on the solution mass flux in achieving cooling effect, owing to the cooling medium flowing inside the tubes. Relatively lower solution pumping power than that of the packed bed contactor can be expected from the fin–tube contactor, in addition to the ability to achieve comfortable and hygienic indoor air at a cooling medium temperature of 17 °C or higher, the ionic liquid desiccant and three-fluid fin–tube contactor pair for liquid desiccant air conditioning system is elevated a step higher as an alternative to vapor compression air conditioning system.

Performance analysis on thermal energy storage unit for an atmospheric water harvester in museum display case

To control the humidity of museum display cases to protect historic relics, a small atmospheric water harvester is proposed for water replenishment which is integrated with a shell-and-tube latent thermal energy storage (LTES) to store off-peak electricity. Numerical models of water harvester with shell-and-tube LTES are established, and an experiment is conducted for model validation. It is indicated that higher inlet air temperature of water harvester brings more collected water, and inlet air temperature of 220 °C can meet the water demand. Heating power and geometrical parameters of shell-and-tube LTES are designed with two adjustable excess factors. The excess factors are found positively related to the outlet air temperature and melting rate in the charging and discharging process. To ensure complete melting of phase change material (PCM), a power excess factor of 1.6 is necessary. The system is tested in a day, and it is demonstrated that water demand of display cases can be met with the designed system. When PCM excess factor is 1.1 and power excess factor is 0.8, maximum annual total cost saving of $1.88 is achieved. The results provide reference for the design of heat storage equipment for atmospheric water harvester.

The Solar Heat Cutting Performance of Double-Skin Facades

The solar heat cutting performance of double-skin facades was analyzed in this paper. A physical model was built to calculate the thermal characteristics of double-skin facades. The effects of location, floor height, facade facing direction, blind slice angle, and skin style on solar heat cutting were investigated. The results show that double-skin facades can effectively cut the heat flux entering room, especially for west facing facade. Comparing with the single-skin facade, the double-skin facade cuts 1410.2 Wh/m2 more heat to enter room for west facing facade in a clear summer day in Nagano, Japan. Floor height mainly influences the outlet air temperature of the facade intermediate space, but not the heat fluxes. Locations somewhat affect the solar fluxes on outer facade surface.

Effect of Geometry and Operational Parameters on the Dehumidification Performance of a Desiccant Coated Heat Exchanger

Solid desiccant dehumidification systems are an alternative to vapor-compression-based air dehumidification systems. They use solid desiccant materials to adsorb air moisture in space cooling. DCHE can integrate the cooling component in the heat exchanger to achieve higher dehumidification capacity. Comprehensive numeric modeling would be necessary to assist in the design and operation of the DCHE under development to achieve maximum performance. This paper provides the details of a heat and mass transfer model developed for this purpose. The model aims to cover a gap in existing models by independently modeling heat transfer on the solid desiccant, fin, and tube. The model results were compared with an experimental reference for validation. The air outlet humidity and temperature results for dehumidification and regeneration showed a deviation lower than 15% from the experiment. The validated model was used to perform a parametric study for a series of design and operating conditions. The parametric analysis showed that an increase of 25% in desiccant layer thickness and thermal contact resistance between solid elements reduces moisture removal by 9.1% and 1%, respectively. These results indicate the need to independently model the desiccant layer.

A novel method for convective drying rate estimation in a deep fixed porous material bed

In this paper, we propose a novel approach to describe the convective drying process of deep fixed porous material beds during the constant-rate drying period, which is based on the equation describing the heat power conservation within the drying zone. In addition, we propose a novel iterative method to solve the equation, which evaluates the outlet air temperature and the drying rate for the bed with given inlet air parameters. The validity of the proposed approach is examined against experimental and CFD numerical modelling data for two cases of biomass beds, namely, sawdust and barley grain, which represent typical porous material drying problems. Furthermore, the analysis of the conservation equation shows that the drying rate of the bed is proportional to the inlet air mass flow rate and is a function of the initial moisture content of the bed; however, it is independent of the bed volume.

Simultaneous application of active and passive methods in cooling of a cylindrical lithium-ion battery by changing the size of the elliptical cavity filled with nano phase change materials

This article performs the numerical study of thermal management of a battery pack using active and passive thermal management methods. For the active method, a forced and laminar airflow is used in the battery pack. For the passive one, phase change material (PCM) is employed around all battery cells placed in the enclosure. The enclosure filled with PCM is elliptical. Four different enclosure models are examined by changing their small diameter. This study is performed when the passive method does not work by melting all PCMs and the active method works. The numerical study method is finite element method and the study is transient. The results demonstrate that the maximum temperature of the battery first enhances and then decreases by employing the active method. The time of the change in the battery temperature trend depends on the enclosure model. The quantity of liquid PCM and the ambient air temperature are also lowered when the active technique is utilized. The temperature of the battery and the quantity of molten PCM are reduced by using enclosures with smaller minor axes. Using cavities with bigger minor axes, on the other hand, increases the quantity of molten PCM and the battery temperature. Also, the air outlet temperature from the enclosure with larger dimensions is higher than other enclosure models.

Numerical Analysis of Geometry Influence on Heat Transfer in a Slotted Fin and Tube Heat Exchanger

The influence of geometric characteristics on thermal and hydraulic performance of slotted fin and tube heat exchangers has been numerically analyzed. Numerical model of a slotted fin and tube heat exchanger has been developed and validated using the experimental data. Considered geometric parameters were fin pitch, fin thickness, and slots height. Air inlet velocities ranged from 1 to 4 m/s, corresponding to Reynolds numbers ranging from 558 to 2234. Total of 56 different cases have been numerically solved and results have been presented in terms of exchanged heat flux, average air outlet temperature, and pressure drop along the heat exchanger. The analysis showed that for the considered operating conditions, an increase in fin pitch results in a slightly higher exchanged heat flux and significant reduction of pressure drop, but after certain value further increase in fin pitch does not result in a noticeable augmentation of exchanged heat flux. Additionally, higher exchanged heat flux was achieved for greater fin thicknesses but causing higher air-side pressure drop. Finally, it was found that the slots height for which a heat exchanger will achieve the highest exchanged heat flux depends on air inlet velocity, however the pressure drop was lower in cases of smaller slots heights.

Microencapsulation of Citronella Essential Oil (Cymbopogon winterianus) with Different Wall Materials Using Spray Drying

Essential oils have flavoring and biological properties such as insect repellency, pesticide properties, antifungal, and bactericidal action. A limiting factor in the application of essential oils in industrialized products is the volatility and thermosensitivity of their components. Microencapsulation is an alternative for using these compounds on a large scale, a technique widely used to protect bioactive compounds against environmental damage. Thus, the objective of the study was to encapsulate the essential oil of Citronella (Cymbopogon winterianus) in different wall materials through the spray drying technique. Three formulations of wall materials were evaluated using: Gum arabic (GA) and maltodextrin (MD), gum arabic (GA) and whey protein concentrate (WPC) powder with 60% protein and maltodextrin (MD), and concentrate whey protein (WPC) powder with 60% protein. The amount of oil in the emulsion was set at 10% (w/v) and the wall materials at 40% (w/v) in a 1:1 ratio. The emulsions were subjected to spray drying using inlet and outlet air temperatures of 120°C and 65-70°C, respectively. The highest microencapsulation efficiency was observed for microcapsules formed by gum arabic (GA) and maltodextrin (MD), which also showed good thermal properties, low humidity, and water activity, important parameters to maintain product stability.

Experimentally validated numerical modeling of heat transfer in crossflow air-to-water fin-and-tube heat exchanger

The aim of this work is to analyze different tube-side inlet boundary conditions in order to properly model heat transfer mechanism in a crossflow air-to-water fin-and-tube heat exchanger (FTHEX). For accurately describing conjugated heat transfer, the entire flow length on both fluid sides should be considered. For problem simplifying, domain that include a segment inside the heat exchanger in the water flow direction, is used. This paper studies the effect of fully conjugated heat transfer, including air-side and water-side thermal resistances. Three different numerical models are analyzed by varying the tube-side inlet boundary conditions. In one of these models the water-side thermal resistance is neglected and other two models consider the water-side thermal resistance, but with different velocity and temperature boundary conditions at the water inlets: uniform and fully developed. To validate the proposed numerical models, measurements have been performed on a crossflow air-to-water plain FTHEX. The results show that the numerical model with the fully developed water inlet boundary condition coincides best with the experimental data. It can be concluded that the water-side thermal resistance cannot be neglected, especially when evaluating the air outlet temperature and the overall heat transfer coefficient of heat exchanger.

Modeling Challenges for Improving the Heat Rate Performance in a Thermal Power Plant: Implications for SDGs in Energy Supply Chains

Rapid industrialization and the increased use of consumer electronic goods have increased the demand for energy. To meet the increasing energy demand, global nations are looking for energy from renewable sources rather than non-renewable sources, to adhere with the sustainability principle. As energy from renewable sources is still in the experimental stage, there is a need to use available energy sources optimally. Considering this, the present study aims to identify, evaluate, and reveal the interrelationship among critical challenge factors in improving the heat rate performance of coal-fired thermal power plants. The study identifies twenty critical challenges through a comprehensive literature review. Then, to evaluate the identified critical challenges, the grey-DEMATEL (Decision Making Trial and Evaluation Laboratory) technique is used. For evaluating the challenges, this study conducts an empirical analysis in a thermal power plant in India. The findings reveal that air preheater leakage, coal flow balancing, and air heater air outlet temperature are the top three critical challenges hampering the thermal power plant’s performance. Additionally, fourteen challenges come under the cause group, while eight challenges come under the effect group. The findings of the study can assist industrial managers in overcoming problems in their thermal power plants. The results can also guide the development of a robust and reliable framework for mitigating these challenges.

Experimental Study on the Performance of a Dew-Point Evaporative Cooling System with a Nanoporous Membrane

In this paper, a plate counter-flow dew-point evaporative cooling system was designed with a nanoporous membrane covered on the surface of the wet channel for enhancement of heat and mass transfer. First, the operating principle of this device and theoretical analysis of nanoporous membrane evaporation were discussed in detail. Then, the impacts of several operating parameters on cooling performance, mainly including inlet air temperature, humidity, velocity, and the effect of utilizing the membrane, were investigated in trials. It was found that the cooling performance can be improved by using membrane significantly. In the dry channel, the maximum temperature decrease can reach 12.5 °C. At a high inlet air temperature, the product air can be dropped to a lower temperature, contributing to a more significant heat transfer process. Lower humidity, on the other hand, resulted in a reduced product air temperature and a lower cooling efficiency. Under the condition of 50% humidity, the wet-bulb efficiency and dew-point efficiency were 1.09 and 0.79, respectively. With the inlet air velocity increasing from 1.5 m/s to 2 m/s, the outlet air temperature would rise, and the wet-bulb efficiency and dew-point efficiency would decrease. To achieve better cooling performance, inlet air velocity ought to be limited to a low speed.

The effect of triangular phase change material rods in the air conditioning duct on the amount of energy required for a residential building

In this paper, a building air conditioning channel was simulated. In the channel, a number of rods made of phase-change material with triangular arrangement were placed. The air flow in the channel melts the phase change material during the day. During the night, the energy stored in the phase change material was used to heat the building. For this purpose, a building was designed and the amount of energy required was estimated using carrier software. This study investigated the effect of PCM rod diameter at different hours on the air outlet temperature as well as the amount of molten PCM. The effect of Reynolds number change was also studied. Fluent software is used for simulation. The results of this study showed that increasing the pipe diameter increases the PCM melting time thus requiring more time for the PCM charge. The effect of changing the inlet temperature on the melting time of PCM in diameter 30 mm is more than other diameters. Changing Reynolds from 200 to 1000 reduces the melting time of PCM in 10 mm diameter rod by 71%. Increasing the inlet temperature but decreasing the PCM melting time and increasing the PCM average temperature. It is possible to use up to 49% of the home heating energy from that system by using the 30 mm pipe in Reynolds 1000 in February, and this amount can be saved in energy consumption.

Modeling of sawdust drying in spouted beds using solar energy and phase change materials

In the present work, the modeling and simulation of the continuous drying of sawdust using spouted beds connected in series and a solar energy accumulator panel to heat the drying air was carried out. The modeling approach for the solar energy accumulator panel was based on energy balances, whereas for the dryer a combination of residence time distribution, drying kinetics and micro-mixing models was considered. Model parameters were adjusted with available experimental data. Simulations results were validated using experimental values, observing that the predicted outlet air temperature of the solar collector presented root mean squared errors lower than 1.9 °C for 5 different air flows, while the outlet sawdust moisture deviated less than 5.6%. Finally, the effect of increasing the number of spouted beds and the solids feed rate on the moisture content leaving the dryer was evaluated, showing a greater influence of the increase in spouted bed units compared to increasing the drying air temperature by 10 °C.

Influence of Dehydration Temperature and Time on Physicochemical Properties of Tomato (Solanum lycopersicum L.) Powder

The purpose of this research was to determine the optimum dehydration temperature and time length for a better physicochemical quality of tomato powders. The treatments consisted of 70, 80 and 90°C dehydration temperatures and 9, 11, and 13 h time durations arranged in a completely randomized design (CRD) with triplicates. The inlet and outlet air temperatures of the hot air oven dryer were about 24 and 60°C respectively with an air velocity of about 2.9 m/s. Fresh tomatoes were used as a control. It has been observed that the major quality parameters of tomato powders were significantly increased with increasing dehydration temperature and time up to 80°C and 11 h respectively. When the dehydration temperature and time length went beyond 80°C and 11 h respectively, the quality of tomato powders declined. The maximum TSS content (7.433 °Brix), titratable acidity (0.4967), rehydration ratio (3.437), lycopene content (0.4512 mg/100 g) and lower pH value (4.433) were obtained at 80°C temperature and 11 h dehydration time. Moisture content was reduced to 11% at the same dehydration temperature and time length without considerable physiochemical quality loss. Inversely, vitamin C was reduced as dehydration temperature and time increased. Generally, the results of this study showed that dehydration of tomatoes with 80°C and 11 h temperature and time length respectively, provides better physicochemical quality of tomato powders. Future research is suggested on consumers' acceptance of dehydrated tomato powders.