Mist Research Articles

Transient analysis of an efficient solar assisted air-conditioning system for subtropical climate with various solar thermal collectors

The air conditioning demand of the world is largely fulfilled by vapor compression systems; however, these systems are also responsible for depleting ozone layer due to the nature of refrigerants. Desiccant cooling systems integrated with solar thermal energy technologies could be an attractive alternative with some performance enhancement techniques. In this study, transient seasonal performance investigation is performed for an innovative solar integrated desiccant cooling system that uses regenerative evaporative cooler known as solar assisted desiccant integrated Maisotsenko cycle cooler for better cooling performance. Furthermore, transient annual performance analysis of solar system for meeting thermal energy requirement for regenerating the desiccant wheel in summer season and handling heating load of the building in winter season is also carried out with three different solar thermal collector technologies for finding out more efficient technology. The key performance indicators in this study are useful energy gain, solar source efficiency, auxiliary energy sharing, coefficient of performance, and solar fraction. The results of the key performance parameters are reported as monthly average values. The proposed integrated system resulted to be very efficient with a maximum COP value of 1.13 in April when latent cooling loads are low and 0.78 in August when latent cooling loads are higher. The system’s maximum cooling capacity is 24 kW in April corresponding to a sensible heat factor of 0.720. Furthermore, the regeneration temperature requirements ranged from 50 °C to 78 °C, respectively that makes it favorable to use low grade thermal energy through non concentrating solar thermal collectors. The regeneration thermal energy requirement for desiccant wheel fluctuates throughout the year, maximizing in August due to higher dehumidification requirements. The study also revealed that the evacuated tube collector technology is most suitable with average annual efficiency of around 36 %.

Evaluation of the shelf life of guava (psidium guajava) stored in a modified scoria evaporative cooler with organic treatments

Guava (Psidium guajava) is a tropical fruit that is highly nutritious but highly perishable. The high perishability rate of the fruit is a clear indication that this fruit requires good post-harvest handling and preservation techniques to prolonging its shelf life. Evaporative cooling technology has been widely adopted for proper storage of perishable products, especially fruits and vegetables. This research was conducted with an objective of evaluating the shelf life of guavas stored in a scoria evaporative cooler in combination with neem extract treatment and beeswax treatment. A portion of the guavas was treated and stored in both ambient and evaporative cooler conditions while the other portion was untreated and stored in both ambient and evaporative cooler conditions. The changes in quality of the guavas over time were evaluated based on the physical, chemical and organoleptic properties of the fruit. The microclimate of the evaporative cooler i.e the temperature and relative humidity, were recorded using a data logger. The shelf life of neem extract treated guavas stored in the evaporative cooler increased by an average of 2 days compared with ambient conditions. For the beeswax treated guava the shelf-life increase by an average of six days compared to the ambient. For untreated guavas the increase in shelf life was 6 days relative to the ambient. The beeswax coated gauvas stored in the evaporative cooler retained the recommended firmness for 5 days more than the ambient. These results show that evaporative cooling combined with beeswax treatment have enormous potential to prolong the shelf-life of guavas significantly. Thus scoria evaporative cooler could be a game changer in post-harvest handing of guavas in rural areas.

Mitigating dengue incidence through advanced Aedes larval surveillance and control: A successful experience from Pakistan.

Dengue fever is a viral disease caused by one of four dengue stereotypes (Flavivirus: Flaviviridae) that are primarily transmitted by Aedes albopictus (Skuse) and Aedes aegypti (L.). To safeguard public health, it is crucial to conduct surveys that examine the factors favouring the presence of these species. Our study surveyed 42 councils across four towns within the Bhakkar district of Punjab Province, by inspecting man-made or natural habitats containing standing water. First, door-to-door surveillance teams from the district health department were assigned to each council to surveillance Aedes species and dengue cases. Second, data collection through surveillance efforts, and validation procedures were implemented, and the verified data was uploaded onto the Dengue Tracking System by Third Party Validation teams. Third, data were analysed to identify factors influencing dengue fever cases. The findings demonstrated the following: (1) Predominantly, instances were discerned among individuals who had a documented history of having travelled beyond the confines of the province. (2) Containers associated with evaporative air coolers and tyre shops were responsible for approximately 30% of the Aedes developmental sites. (4) Variability in temperature was responsible for approximately 45% of the observed differences in the quantity of recorded Aedes mosquito developmental sites. (5) Implementation of dengue prevention initiatives precipitated a 50% reduction in Aedes-positive containers, alongside a notable 70% decline in reported cases of dengue fever during the period spanning 2019 to 2020, while the majority of reported cases were of external origin. Aedes control measures substantially curtailed mosquito populations and lowered vector-virus interactions. Notably, local dengue transmission was eliminated through advanced and effective Aedes control efforts, emphasising the need for persistent surveillance and eradication of larval habitats in affected regions.

Experience of using evaporative cooling of graphitized electrodes to reduce their consumption in ore smelting furnaces

Consumable graphitized electrodes (GE) are widely used for supplying current to AC and DC EAF's, ore-smelting and indirectly heated electric arc furnaces. Due to large current, thermal and mechanical loads, their consumption in the structure of the cost of smelting in some cases, for example, in steel smelting reaches 30 %. Considering this, as well as the unstable global economic situation, when many enterprises use imported electrodes, solving the issue of reducing them is urgent. Foreign-made arc steel furnaces with a capacity of 100 tons and more successfully use evaporative cooling (EC) technology. Its use leads to a reduction in graphite consumption by an average of 10–15 %. However, for ore-thermal furnaces, no data on the experience of using EC GE has been found in the literature. The purpose of the work is to study the possibility of reducing the temperature and consumption of GE in arc ore-smelting furnaces when using EC technology. Experimental studies were carried out at the enterprise PC “AVISMA” (Berezniki), which includes three ore-smelting furnaces with a capacity of 100 tons. For the graphite electrodes used in these furnaces, modeling of their thermal state was performed with and without EC. Rational technological parameters of the cooling process were determined: water flow 1.5 m3/h and system turn-on time 5–15 minutes from the start of the current supply. An experimental design of the EC ring and a system for monitoring water and air flow have been developed. As a result of several heats, a decrease in the surface temperature of the GE was recorded when using EC with water on its side surface and a number of shortcomings were identified. Recommendations for improving technology and improving the design of the AI system are formulated

Minimum Air Cooling Requirements for Different Lithium-ion Battery Operating Statuses

Abstract Batteries play an important role in increasing the use of renewable energy sources. Owing to the temperature sensitivity of lithium-ion batteries (LIBs), battery thermal management systems (BTMSs) are crucial to ensuring the safe and efficient operation of LIBs. Researchers have mainly focused on evaluating the performance of BTMS; however, little attention has been paid to the minimum cooling requirements of LIBs, which are important for optimizing the design and operation of BTMSs. To bridge this knowledge gap, the aim in this study was to determine the minimum air cooling requirements for different LIBs operating statuses based on computational fluid dynamics simulations. The inlet airflow rate had the strongest influence. For the studied cases, when the battery operates at charge/discharge (C) rate of three or below, the inlet temperature should be set below 35 °C, and the gap between the batteries should be greater than 3 mm to meet the minimum heat dissipation requirement. At a C-rate of 0.5C, natural convection is sufficient to meet the cooling needs, whereas at 1C or higher rates, forced convection is required. Increasing the number of batteries from six to eight has little impact on the inlet flow required to accommodate the battery heat dissipation.

Assessment of evaporative porous clay cooler for Building-Integrated photovoltaic systems via energy, exergy, economic and environmental approaches

A thorough study has been conducted for the energy, exergy, economic and environmental analysis to investigate the feasibility of utilizing an evaporative porous structure cooler for the building-integrated photovoltaic (BIPV) system at different building’s sides and directions. Photovoltaic panels within the BIPV systems dissipate their heat to the building’s sides which contribute to rise the interior building’s temperature. In the proposed system, a water-saturated evaporative porous clay cooler is being installed on the back surface of the PV panels to absorb and dissipate their heat by latent evaporation through an evaporation cooling process. A transient numerical heat and mass transfer model based on energy, exergy, economic and environmental approaches was proposed to assist the feasibility of cooling BIPV system via evaporative porous structure cooler. The model was also validated experimentally in the present study. The results exhibited that, comparing with conventional BIPV systems, the presented BIPV/Clay cooling system achieved a peak photovoltaic temperature reduction of 19.1 °C, with a maximum enhancement in the photovoltaic system’s electrical efficiency, electrical power, and exergy efficiency of 9.8 %, 12.6 % and 11.8 %, respectively. The ultimate reduction in the building’s annual thermal load was around 53.8 % when the clay evaporative cooling approach is applied, while the cost of electricity production reduced ultimately by 7.9 %, (from 0.151 $/kWh to 0.134 $/kWh). Further, the payback period decreased by 2.33 years and the annual amount of CO2 emissions decreased by 10.4 % for the utilized BIPV/Clay cooling system compared with the conventional BIPV system.

The Best Design for a Direct Evaporative Cooling System Based on Pressure Drop at Desired Saturation Efficiency: A Cost–Benefit Optimization

The Best Design for a Direct Evaporative Cooling System Based on Pressure Drop at Desired Saturation Efficiency: A Cost–Benefit Optimization

Sistem Kontrol Otomatis dan Efesiensi Energi Listrik dari Penggunaan Air Cooler Berbasis IOT

Air Coolers are the right choice as an air conditioning tool compared to AC because they are much more energy efficient and environmentally friendly. In this system, the Air Cooler on/off function will be controlled automatically based on the room temperature detected by the DHT22 sensor. If the room temperature reaches 24o Celsius, the Air Cooler will be off. Then this automatic system is also able to control the on/off of the Air Cooler based on the number of people entering and leaving the room using the IR Proximity sensor. The Blynk application connected to a smartphone allows for regular monitoring of the voltage and current used by the Air Cooler. Then a comparison of the electrical energy used by the Air Cooler is carried out before and after using the system that has been designed. The conclusion obtained is that the system designed is able to control automatically and save electrical energy from using the Air Cooler.

Utilizing Reversed Brayton Cycle for Enhanced Cooling Tower Technology

This study demonstrates an enhanced cooling tower technology (ECTT) under which the ambient air is precooled and dehumidified to improve the cooling tower efficiency. The reverse Brayton cycle, comprising a compressor, an air cooler, an expander, and a heat and mass exchanger, is used to precondition the ambient air before entering the cooling tower. A plant-scale thermodynamic model is constructed for ECTT, and the system parameters are optimized through genetic algorithm based on the maximum power gained from the system, including the effects of reducing the makeup water for the cooling tower. Compared to conventional cooling towers, the ECTT achieved sub-wet bulb cooling of water, which is 9.5 °C below the wet bulb temperature of ambient air, reduces steam condensation temperature by 34%, and increases steam turbine power output by 4.3%. It also reduces evaporative losses in the cooling tower and reduces the makeup water by 36%. With cooling tower exhaust recirculated in a closed loop, makeup water requirements are further reduced with additional gains in power output.

Numerical Analysis on Performance Improvement of a Vertical Plate Indirect Evaporative Cooler with Baffles

The performance of the Plate Indirect Evaporative Cooler (PIEC) can be effectively improved by incorporating baffles in the dry channel. However, in the dimensional influence of the baffles on PIEC performance there remains a research gap. In order to investigate the impact of baffle dimensions on the wet bulb efficiency, namely the average heat transfer coefficient and the cooling capacity of the PIEC, this paper proposed and verified a three-dimensional numerical model and method based on the species transport model and the Euler wall film model. At the same time, in order to obtain the equilibrium point between the enhanced heat transfer performance and the additional resistance induced by baffles, a comprehensive performance evaluation index is introduced. The results indicate that, under the same conditions, (1) the baffle effect on PIEC performance is significant at a lower inlet air velocity, and the wet bulb efficiency of the PIEC with baffles can be improved by 22.8%; (2) the baffle effect on PIEC performance is negative if its relative length exceeds 60% or the primary air inlet velocity surpasses 4 m/s under the conditions specified in this paper; and (3) the baffle effect on PIEC performance is significant when its channel height is lower and its channel width is larger, and the wet bulb efficiency of the PIEC with baffles can be improved by 29.3%.

Performance Analysis for Battery Stability Improvement using Direct Air Cooling Mechanism for Electric Vehicles

Safety concerns about the battery are primary challenges for the maker of the electric vehicle (EV) system. At continuous work, maintaining the optimal temperature is a crucial scientific issue. It has restricted the widespread use of batteries. Hence, maintaining the optimal temperature for E-vehicles has been analyzed in this study. To achieve more energy density in charging, the discharging cycle and compact structure have been essential. In this study, a direct air-cooling system has been addressed to reduce the temperature of the battery pack, resulting in a significant improvement in system efficiency. The 1.44 kgwatt (kW) battery back has been constructed for the E-vehicle by Simulink diagram to analyze the system. In this study, two various scenarios have been made, such as with air cooling and without cooling, to validate the outcomes. Torque and speed characteristics have been analyzed for this study. Air-cooling-based batteries for e-vehicle simulation have delivered better outcomes, such as high power charging and discharging and a discharge depth of 92%. The differential battery pack temperature has been reduced by increasing the cooling air flow rate to 2 ms−1, 4 ms−1, and 6 ms−1. To attain an even delivery of coolant air flow, a design criterion has been suggested. The outcome of the study has been evaluated through numerical analysis.

A novel CFD model for design and performance prediction of recuperators for Indirect Evaporative Cooling

Indirect evaporative cooling (IEC) appears to be a highly promising technology for incorporating and/or substituting traditional air conditioning systems, as it can guarantee good cooling performance with a reduced environmental impact. In this study, a Computational Fluid Dynamics (CFD) model for design and performance prediction of recuperators for IEC systems with dry primary and secondary channels was developed. The model was validated against experimental data for a cross-flow recuperator, obtaining a maximum difference between numerical and experimental results of 4.9% for the secondary air outlet temperature, 5.3% for the primary air outlet temperature, and 8.1% for the dry-bulb effectiveness. After validation, the model was used to find a new plate geometry which guarantees a 12.5-15.9% improvement in the dry-bulb effectiveness, without an excessive increase in the pressure losses along the channels.

Experimental assessment of the energy performance of a renewable air-cooling unit based on a dew-point indirect evaporative cooler and a desiccant wheel

Given the escalating energy consumption in cities worldwide, it is crucial to investigate the utilization of sustainable technologies and renewable energy sources. The number of empirical studies on the energy performance of hybrid air-cooling systems is limited. Therefore, the objective of this work is to experimentally study the energy performance of a novel renewable air-cooling unit. This prototype is mainly composed of a desiccant wheel and a dew-point indirect evaporative cooler to independently control the temperature, humidity, and carbon dioxide levels of indoor air. 64 experimental tests are carried out to fit an empirical model of this renewable air-cooling unit, focusing on outlet air conditions and the coefficient of performance. In addition, several performance indices are developed for desiccant wheel and dew-point indirect evaporative cooler: (i) moisture removal capacity; (ii) moisture removal capacity per unit of electrical power-consumption; (iii) dew-point efficiency and (iv) cooling capacity of dew-point indirect evaporative cooler per unit of electrical power-consumption. The highest values of dehumidification capacity, sensible cooling capacity and coefficient of performance for this renewable air-cooling unit are achieved for the most severe outdoor air conditions, namely 19.02 kg·h−1, 21.49 kW and 11.0, respectively. This work can serve as a reference for research on the feasibility of hybrid air-cooling systems in the scenarios of heat events and climate change world.

BATTERY COOLING SYSTEMS OF ELECTRIC VECHILES

To enhance electric vehicle battery performance, the Battery Thermal Management System (BTMs) plays a crucial role by regulating internal battery temperature within optimal limits. Among the key components, the cooling system is paramount in maintaining this temperature range. Various cooling techniques such as Air Cooling (AC), Liquid Cooling (LC), Refrigerant Direct Cooling (RDC), Phase Change Material (PCM) based systems, Thermoelectric Cooling (TC), Heat Pipe Cooling (HPC), and Hybrid Cooling (HC) have been employed in electric vehicles. This paper provides an exhaustive review of these cooling systems, delineating their respective merits and demerits. The findings offer valuable insights for researchers delving into electric vehicle battery cooling technology. Keywords: Electric vehicle, battery, cooling system, thermal management system.

Micro and macro urban heat islands in an industrial city: Bradford, UK

The urban heat island (UHI) phenomenon refers to the temperature difference(s) between urban/built environments and suburban/natural areas. It affects energy use, health, water quality, and in brief, the quality of life in cities. Understanding the magnitude of this issue could help urban planners and decision makers to better implement green interventions into their cities. This paper shows the results of field measurements carried out to study the UHIs in Bradford, as one of the most deprived cities in the UK with minimum green infrastructure. In the first phase of the study, air temperatures were measured in twenty locations (four areas) with different land covers in Bradford. These measurements were called micro UHI study, as the air temperatures were measured in areas within the boundaries of the city. Data were collected in late summer and early winter. The results showed that the UHI is more sensible in the colder day (with average 0.6 °C cooler air temperature in a green area compared to the city centre). Greener areas experienced higher wind and lower air temperatures compared to dense urban settings in December. In the second phase of the study (macro scale), diurnal air temperatures from a residential (urban) versus a rural site were compared during a heat wave episode (seven days). It was observed that the rural site was 0.8 °C cooler than the residential/urban site. The maximum temperature differences occurred during the nights/early mornings between the two sites (3.2 °C at 5:00am).

Siberian vegetation growth intensifies monsoon precipitation in southern East Asia in late spring and early summer

Regional hydrological cycle responding to rising temperatures can have significant influences on society and human activities. We suggest a new perspective on East Asia’s enhanced precipitation amount that emphasizes the role of Siberian surface warming. Increased vegetation greenness in late spring and early summer in eastern Siberia, which may be a response to global warming, acts to warm the surface by reducing the surface albedo with an increase in net absorbed shortwave radiation. Subsequently, eastern Siberia warming leads to the strengthening of anti-cyclonic atmospheric circulation over inner East Asia as well as the subtropical western North Pacific high via thermal forcing and the enhanced land-sea thermal contrast, respectively. Consequently, the anticyclonic circulation over inner East Asia transports much drier and cooler air to southern East Asia. This leads to favorable conditions for increased precipitation in combination with an increased tropical moisture flux from the subtropical western North Pacific high. Therefore, continuous Siberian vegetation growth has a potential influence on the future precipitation amount in the subtropics through vegetation–atmosphere coupled processes.

Local Entropy Generation Analysis of the Counter-Flow Dew-Point Evaporative Coolers

Abstract A comfortable indoor working circumstance can be accomplished by a ventilation and air conditioning system. There are several factors influencing the quality of indoor air, with the insufficiency of ventilation accounting for over 50% of the overall considerations. While traditional air conditioner is able to fulfill the needs of ventilation and indoor temperature control, low-efficiency and high energy consumption no longer align with the current sustainable and energy-efficiency goals. Thus, the development of energy-saving and high-efficiency air conditioning systems is crucial for realizing green and efficient building practices. Evaporative cooling technology, specifically dew-point evaporative cooling, has garnered extensive attention as an efficient cooling method and a candidate for environmentally friendly and high-performance alternatives to traditional air conditioning systems. This article investigates the thermodynamic losses involved in a dew-point evaporative cooling system using the counter-flow design. Detailed mathematical models for the evaporative cooler along with the entropy generation in the channels are developed. The model facilitates calculations of (1) the entropy generation distribution in different layers within the system and (2) the entropy generation of each layer and the whole system under various input conditions. Approaching the system from the second law of thermodynamics perspective, this model serves as a guide for selecting the optimal operating conditions, thus promoting the widespread application and commercialization of dew-point evaporative cooling systems with the counter-flow structure.

Optimizing electricity generation through the utilization of wasted heat from process streams in a LURGI methanol plant

In the realm of petrochemical operations, persistent efforts have been made to curtail specific energy consumption; however, certain heat sources continue to be underutilized. This paper investigates the condition of a Lurgi methanol plant to identify process streams with enough wasted heat that have the potential to produce electricity. After a thorough analysis, one particular zone is identified where an air cooler package and seawater exchanger are used to decrease the temperature of crude methanol vapor. To harness this untapped heat for electricity generation, an organic Rankine cycle (ORC) is proposed. In the quest for efficient electricity production, three distinct working fluids-dry (R600a), wet (R134a), and isentropic (R11)- are scrutinized to compare their performance in generating electricity within the ORC system. In addition, the maximum amount of electricity that can be generated from this waste heat recovery (WHR) project is determined and optimized using a multi-objective optimization method. By leveraging genetic algorithms, the system's exergy is enhanced while minimizing costs. A comprehensive economic comparison is conducted using probability analysis to evaluate each system's financial viability. The results show that dry and isentropic working fluids yield the best results for electricity production, generating approximately 9–10 MW. The return on investment (ROI) for these working fluids is also nearly similar, at 16 %. Among the chosen working fluids, R600a is selected as the superior option due to its lower outlet temperature for crude methanol. Additionally, because the cooling water flow for the condenser of the ORC is identified as a limitation in the current petrochemical plant, a new optimization is conducted with a constraint on the flow of cooling water, aiming for approximately 3000 tons/h. The results show that the proposed WHR-ORC system can generate a maximum of approximately 7.5 MW net electricity in the studied petrochemical plant, while also reducing CO2 emissions by up to 40,000 tons per year. The innovative methodology showcased in this research underscores its economic viability, paving the way for heightened energy efficiency and environmentally conscious methanol production practices.

Effect of the plates geometry on the performance of a cross-flow recuperator for indirect evaporative cooling systems

In recent years, Indirect Evaporative Cooling (IEC) is becoming a very interesting technology, as it can guarantee a good cooling effectiveness with low energy demand, thus helping to face the issues of climate change. In this work, a Computational Fluid Dynamics (CFD) model has been used to evaluate the effects of the plates geometry on the performance of a recuperator for IEC systems with dry primary and secondary channels. The model was validated against experimental data for a cross-flow IEC system with dimpled plates, and the validation results were quite satisfactory. Therefore, five types of dimpled plates differing from the original one in shape and size of the dimples were investigated. The results showed that a good trade-off between the improvement of dry-bulb effectiveness and restrained pressure losses along the channels is obtained with dimples in the shape of right prisms with either triangular, or pentagonal, or circular base section, depending on the application.

Efficiency Analysis of a Two-Stage Evaporative Cooling System with Sustainable Water Pad

Efficiency Analysis of a Two-Stage Evaporative Cooling System with Sustainable Water Pad