EC Directive Research Articles

Evaporative Cooling Options for Building Air-Conditioning: A Comprehensive Study for Climatic Conditions of Multan (Pakistan)

This study provides comprehensive details of evaporative cooling options for building air-conditioning (AC) in Multan (Pakistan). Standalone evaporative cooling and standalone vapor compression AC (VCAC) systems are commonly used in Pakistan. Therefore, seven AC system configurations comprising of direct evaporative cooling (DEC), indirect evaporative cooling (IEC), VCAC, and their possible combinations, are explored for the climatic conditions of Multan. The study aims to explore the optimum AC system configuration for the building AC from the viewpoints of cooling capacity, system performance, energy consumption, and CO2 emissions. A simulation model was designed in DesignBuilder and simulated using EnergyPlus in order to optimize the applicability of the proposed systems. The standalone VCAC and hybrid IEC-VCAC & IEC-DEC-VCAC system configurations could achieve the desired human thermal comfort. The standalone DEC resulted in a maximum COP of 4.5, whereas, it was 2.1 in case of the hybrid IEC-DEC-VCAC system. The hybrid IEC-DEC-VCAC system achieved maximum temperature gradient (21 °C) and relatively less CO2 emissions as compared to standalone VCAC. In addition, it provided maximum cooling capacity (184 kW for work input of 100 kW), which is 85% higher than the standalone DEC system. Furthermore, it achieved neutral to slightly cool human thermal comfort i.e., 0 to −1 predicted mean vote and 30% of predicted percentage dissatisfied. Thus, the study concludes the hybrid IEC-DEC-VCAC as an optimum configuration for building AC in Multan.

Simulation-based performance analysis of residential direct evaporative coolers in four climate regions of Iran

In this paper, the effect of direct evaporative cooling (DEC) system design parameters, including the cooling pad saturation efficiency, the airflow rate, and the thermostat set-points on the system electricity and water consumption, is evaluated in four different climates of Iran according to Köppen-Geiger classification. EnergyPlus is used to perform the simulations for a typical residential apartment. The results show that using pads with a 30% higher saturation efficiency can significantly decrease the electricity and water consumption by up to 50.0% and 29.6%, respectively, because of the working time reduction. The maximum impact is in Esfahan city in cold desert climate as its wet-bulb temperature is lower than other investigated climates. Besides, increasing the airflow rate from 3000 m3/h to 6000 m3/h leads to 43.4%–55.2% reduction in electricity consumption in different climates, although the water consumption increases by 20.5%–58.8%. According to the results, by using the DEC system with 80% saturation efficiency and 6000 m3/h airflow rate, the average indoor relative humidity and CO2 concentration is 42.3%–48.5%, and 450 ppm–470 ppm, respectively, in different climates, which can provide acceptable indoor air quality. Increasing the saturation efficiency or decreasing the airflow rate increases the indoor relative humidity and CO2 concentration. The results are also compared with a typical packaged terminal air conditioner (PTAC). The total hours when the indoor relative humidity is out of comfort zone in the DEC system, with 60% saturation efficiency, are about 92% lower than the PTAC system, on average. Moreover, with 24/26 °C thermostat set-points, the PTAC system consumes 234%–265% more electricity than the DEC one with 80% saturation efficiency in different climates.

Experimental study of a direct evaporative cooling approach for Li‐ion battery thermal management

Author(s): Zhao, R; Liu, J; Gu, J; Zhai, L; Ma, F | Abstract: A desirable operating temperature range and small temperature gradient is beneficial to the safety and longevity of lithium-ion (Li-ion) batteries, and battery thermal management systems (BTMSs) play a critical role in achieving the temperature control. Having the advantages of direct access and low viscosity, air is widely used as a cooling medium in BTMSs. In this paper, an air-based BTMS is modified by integrating a direct evaporative cooling (DEC) system, which helps reduce the inlet air temperature for enhanced heat dissipation. Experiments are carried out on 18650-type batteries and a 9-cell battery pack to study how relative humidity and air flow rate affect the DEC system. The maximum temperatures, temperature differences, and capacity fading of batteries are compared between three cooling conditions, which include the proposed DEC, air cooling, and natural convection cooling. In addition, a DEC tunnel that can produce reciprocating air flow is assembled to further reduce the maximum temperature and temperature difference inside the battery pack. It is demonstrated that the proposed DEC system can expand the usage of Li-ion batteries in more adverse and intensive operating conditions.

Do non-metallic material and radiation shields affect the operation of direct evaporative cooling systems?

The evaporation phenomenon is used as a passive cooling approach to absorb the sensible heat and convert it into the latent heat. The usage of evaporative cooling systems has boomed, recently, because of its low operational cost. The Direct Evaporative Cooling (DEC) systems can be used widely in warm dry environmental conditions, such as Middle East countries. Several factors can affect the DEC system such as water temperature, evaporative cooling pad thickness, air velocity, and solar radiation flux. In this study, the performance and water consumption of evaporative-based cooler manufactured by RFX Polycarbonate-Structured Sheet (PSS) are compared with the metal-casing one. The impacts of tilting the roof of the cooler and attaching a glass wool-aluminum foil on the cooler are evaluated. The assessments show about 20.6% reduction in the usage of water for the case of RFX Polycarbonate-Casing cooler compared to the metallic material. Results also revealed that tilting the roof saves 29% water compared with the metal-casing cooler while changing the inclined roof to the glass wool-aluminum foil radiation shield further saves the water by about 25%. The performance of the RFX-PSS cooler is enhanced by about 4.7% as compared to the metal-casing cooler. The improvement of 8.1% occurs by tilting the roof in RFX Polycarbonate-Casing cooler in comparison with the metallic DEC system and attaching the isolation foil of glass wool-aluminum instead of the inclined roof increases the saturation efficiency by 7%.

Energy Performance Comparison between Two Liquid Desiccant and Evaporative Cooling-Assisted Air Conditioning Systems

This study investigated the annual energy saving potential and system performance of two different evaporative cooling-based liquid desiccant and evaporative cooling-assisted air conditioning systems. One system used an indirect and direct evaporative cooler with a two-stage package to match the target supply air point. The other was equipped with a single-stage, packaged dew-point evaporative cooler that used a portion of the process air, which had been dehumidified in advance. Systems installed with the two evaporative coolers were compared to determine which one was more energy efficient and which one could provide better thermal comfort for building occupants in a given climate zone, using detailed simulation data. The detailed energy consumption data of these two systems were estimated using an engineering equation solver with each component model. The results showed that the liquid desiccant and dew-point evaporative-cooler-assisted 100% outdoor air system (LDEOAS) resulted in approximately 34% more annual primary energy consumption than that of the liquid desiccant and the indirect and direct evaporative-cooler-assisted 100% outdoor air system (LDIDECOAS). However, the LDEOAS could provide drier and cooler supply air, compared with the LDIDECOAS. In conclusion, LDIDECOAS has a higher energy saving potential than LDEOAS, with an acceptable level of thermal comfort.

EXPERIMENTAL INVESTIGATIONS OF EVAPORATIVE COOLING SYSTEM FOR BUILDINGS UNDER HOT AND DRY ENVIRONMENTAL CONDITIONS

The performance of one-stage direct evaporative cooler (DEC) and two-stage indirect-direct evaporative cooler (IEC−DEC) in the environment of Saudi Arabia is assessed experimentally. The wet pad used in direct evaporative coolers is one of the main parts affecting the output of an evaporative cooler. In this study, three combinations of pad materials: a combination of aspen fiber and corrugated cellulose (Case-I), corrugated cellulose (Case-II), and aspen fiber (Case-III) were focused as a wet media for water evaporation and the performance of these pad materials was analyzed in detail. The main design parameter considered is the water fl ow rate in the designing of both coolers. During the testing of both coolers the ambient temperature in the range from 28°C to 42°C and relative humidity lower than 65% were considered to cool the working air. The air temperature and relative humidity were measured and the eff ectiveness of the coolers was determined. The results obtained show that eff ectiveness of the IEC−DEC system is in range of 95−110%, while that of DEC amounts to 85−93%. As an overall the IEC−DEC system with pad material of Case-I showed a comparatively better performance.

Physico-chemical characteristics of some Indian and Yemeni Honey

The present study aimed to evaluate the physio-chemical properties of four Indian and Yemeni types of honey Coorg and Kashmiri honey (India), Sidr and Acacia honey (Yemen). The honey samples appeared to conform to the European Legislation (EC Directive 2001) for most of the parameters. The moisture content of the samples varied between 13.5 to 19.5g/100g, Indian honey were the highest moisture content. PH values ranged between 4.7 to 5.6, all tested samples were light acidic. Electrical conductivity ranged from 0.13 to 1.4mS /cm. The color intensity values ranged between 137.3 to 624.7mAU. HMF content fluctuated between 15.4 to 19.9 mg / kg. The ash content varied from 0.05 to 0.68%. The total protein content varied between 0.61 to 1.9 %. The diastase activity values ranged between 9.6 to 11.9 DN. The Kashmiri honey showed the highest value of reducing sugars (64.6 g/100g), while Acacia honey showed the lowest value (59.9 g/100 g) The estimated fructose/glucose ratio for all investigated samples was ranged from 1. 03 to 1.37 and estimated glucose/water ratio was ranged from 1.48 to 1.90. Potassium was found to be the predominant mineral in all honey tested. The highest Potassium content (2176.4 mg/kg) was found in Sidr Yemeni honey. The heavy metals were not detected in all honey samples, that the tested honey was safe for human consumption. The results suggest that Indian and Yemeni honey could be beneficially used as a functional or nutraceutical substance.

A feasibility assessment of single to multi/hybrid evaporative coolers for building air-conditioning across diverse climates in India

This paper assesses the potential of direct evaporative cooling (DEC), indirect evaporative cooling (IEC), direct expansion system (DX) and their different combinations (IEC-DEC, DEC-DX, IEC-DX, IEC-DEC-DX) for building air-conditioning of a 8-story residential building containing 32 flats for 21 cities belonging from five climatic zones in India. The building layout and type of air-conditioning module are designed in DesignBuilder integrated with EnergyPlus, and assessed daily (May, 20th) and yearly (Jan, 01st - Dec, 31st) variation of building performance for several climatic conditions. Although the IEC-DEC attains a maximum coefficient of performance (COP) up to 7 for the cities like Amritsar and Nagpur, the IEC-DEC-DX is found ideal for all climatic zones due to higher average wet-bulb effectiveness and cooling capacity around 150% and 400 kW, respectively. Moreover, the energy saving potential of IEC-DEC-DX comparing to conventional DX system is observed up to 25%. Considering the pre-eminence of IEC-DEC-DX, a yearly assessment of cooling capacity, energy consumption, COP, life-cycle cost and CO2 production are conducted. A case study based on climatic conditions of Hyderabad by maintaining the predicted mean vote (PMV) within the range of ±2 is conducted to estimate the payback period of the proposed various cooling modules with respect to conventional DX system.

Personalized Evaporative Cooler to Reduce Energy Consumption and Improve Thermal Comfort in Free-Running Spaces

The need to reduce energy consumption in buildings is imperative, but we must maintain individual thermal comfort of the occupants to ensure their well-being and productivity. Personal conditioning systems (PCS) have been suggested as a strategy to achieve both energy efficiency and thermal comfort, as they are considered to be low-energy consumers, allow increasing set-point temperatures, and give occupants the chance to control their own personal environment. While most warm-environment PCS are based on air-movement devices, the potential of using desk direct evaporative coolers (dDEC) has been scarcely explored. This work presents the results of the characterization of a dDEC and its potential for improving the indoor temperature and thermal comfort in a free-running office space. The study proposes adapted corrective power (CPa) and cooling fan efficiency for evaporative systems (CFEe) indexes. Results show that the dDEC achieves thermal comfort with a local effect, and it is recommended to be positioned directly on the desk surface, orientated to the occupant, and at a certain distance. Under these conditions, the CPa reaches −2.8 °C, involving better CFEe than the desk fans studied in the literature. Speed has little effect on the local air conditions, though it does improve the perception of thermal comfort. The relative humidity of the air does not exceed the recommendable limits, but renovation of the indoor air enables better conditions.

Improving flood risk map accuracy using high‐density LiDAR data and the HEC‐RAS river analysis system: A case study from north‐eastern Romania

AbstractNorth‐eastern Romania is frequently affected by storms that produce annual floods with catastrophic effects upon agriculture areas. The implementation of the 2007/60/ EC Directive, which aims, among other things, to assess and manage flood risk, is currently being carried out by means of rough hydrological risk maps. Additionally, the limits of the potentially floodable areas generated on digital elevation models with 30 points/m resolution (SRTM) do not correspond to the current topographic reality. Three tests (T1, T2, and T3) for modelling the floodplains and the comparative assessment of potential damages in the case of 30 localities in the study area (Başeu River basin) were carried out in this study. The results indicate that official data (T1) underestimate potential damage in the case of hydrological events with a recurrence interval probability of 1% (100‐year). The T2 [1%] (100‐year) results also highlight the role of hydro‐technical works in mitigating floods. In T3, the hydrological risk areas were generated with an accuracy of 0.5 m, evaluating the probable damage in cases of events with probabilities of 3% (33.3‐year), 1% (100‐year), and 0.1% (1,000‐year) recurrence intervals. The accuracy of the official hydrological hazard maps (T1) was improved using high‐density LiDAR data and HEC‐RAS software (T3).

Experimental investigation of energy and exergy performance of a direct evaporative cooler using a new pad type

In this paper a comprehensive experimental parametric study on the performance of a new evaporative cooling pad type made of cellulose papers in bee-hive structure is presented. Four different pad sizes of face area 0.335 × 0.390 m2 and thicknesses 35, 70, 105, and 140 mm are examined. The tests are carried out in a wind tunnel adapted with the evaporative cooling system. Experiments are conducted to evaluate the cooling pad performance parameters: air temperature drop, air humidity ratio raise, cooling capacity, water evaporation rate, saturation efficiency, pressure drop, energy efficiency, energy efficiency ratio, exergy efficiency and overall exergy efficiency. The effects of the cooling pad thickness and the operating conditions including air velocity, inlet air temperature, water flow rate, water temperature and cooling pad thickness on the performance parameters are investigated. The results show that, the saturation efficiency, exergy efficiency and overall exergy efficiency of the proposed pad enhance with increasing the pad thickness and water flow rate and their highest obtained values are 84%, 92% and 74%, respectively. The maximum pressure drop, temperature drop and cooling capacity obtained for this pad are 46 Pa, 18 °C and 6.26 kW, respectively. Moreover, the highest energy efficiency ratio is 281 obtained at 2 m/s air velocity. Finally, new dimensionless experimental correlations for predicting the system performance parameters in terms of various operating conditions and system size are presented.

Ro-Ro Kargo Gemisi İçin Tanımlanan Kurutuculu Buharlaşmalı Soğutma Sistemlerinin Termodinamik Analizi

This study presents the results of thermodynamic feasibility of the new desiccant- evaporative- cooling system for an air conditioning application in ships. The desiccant- evaporative- cooling system is characterized by energy efficiency and low environmental impact. In this work, thermodynamic possibility to install desiccant cooling system (DCS) has been studied for a M/V ASSTAR Trabzon Ro-Ro cargo vessel, by using fraction of the heat rejected by existing on-board engine. The baseline system is incorporated a desiccant dehumidifier, a heat exchanger, an indirect evaporative cooler, and a direct evaporative cooler. The system offered sufficient sensible and latent cooling capacities for a wide range of climatic, while allowing in flux of outside air in excess of what is typically required for Ro-Ro cargo vessel. The present work aims at identifying the parameters of the system cycle and investigates their effect on the performance of the waste-heat driven cooling systems. And, the effect of different return air flow rates usage on the system performance is another aspect of the study. Two approaches for mixing of the return air and outside air are introduced; one is consists of two recirculation cycles, other one is a ventilation cycle, all of them have been examined and demonstrated. The maximum coefficient of performance (COP) of a waste-heat driven cooling cycles were determined by assuming that the cycles are totally reversible.

Performance Enhancement of Evaporative Cooling by using Bamboo

In daily life Air-conditioning plays an essential role in ensuring human thermal comfort. The commercially used cooling systems are intensively power consuming. So that it is necessary to save the energy in air conditioning. Among all of them the evaporative cooling techniques is well known which gives better result in saving energy and it is environmental friendly techniques. Evaporative cooling uses the fact that the water will absorb a relatively large amount of heat in order to evapor ate. The temperature of dry air will dropped because of phase change water into water vapors. Evaporative cooling requires abundant water and it works best when relative humidity is low. Evaporative cooling will be done using three methods direct evaporativ e cooling, Indirect Evaporative cooling, combined direct-indirect evaporative cooling. The main aim of this paper is to make comfort condition in terms of Temperature and Humidity and to minimize the water consumption. In this paper at a place of dry grass or cooling pads we are using hollow bamboo as fluid conduit. In hollow bamboo water continuously flows without any restriction. Some slits or holes are provided on the bamboo to enable the water and air contact and ease the evaporative action after CFD flow simulation. After providing such geometry of contact the evaporation comes to optimism and the water consumption as well as humidity is reduced, the continuous flow of water inside hollow bamboo reduce the contact time of water with air. Due to this effect the humidity of air is comparatively less than direct contact evaporative cooler, also reduces the water consumption. This type of evaporative cooler is designed to facilitate efficient evaporation of the water and circulation of cooled air.

Performance Analysis of a Desiccant Evaporative Cooling System for Mango Fruit Storage in the Savannah and Transitional Zones of Ghana

Abstract Performance analysis of a 1.0 tonne desiccant evaporative cooling storage structure for mango fruits was studied. The study examined the effects of inlet air conditions and water flow rates through an absorber on the cooling performance of the system. The airflow rate was approximately 0.24 m3·s−1 and water flow rates through the absorber varied from 0 to 0.252 l·s−1. The system produced approximately 7 kW of cooling at water supply rate of 0.252 l·s−1. A simple linear correlation was established for condition line slope from inlet to exiting air conditions for all the water flow rates. Lines of best fit resulted in correlation coefficient better than 0.96. The observed temperatures with a direct evaporative cooler, tested with freshly harvested mango fruits were found to be between 15.1°C and 23.4°C and relative humidity between 81.8% and 97.7%. Physiological weight loss and firmness assessments of the fruits were also conducted.

Performance investigation of ground source heat exchanger with desiccant-based hybrid cooling system in humid climate

A desiccant-based hybrid cooling is among the most cost-effective air conditioning systems. The main purpose of this paper is the assessment of the potential of ground-assisted direct evaporative cooler together with a desiccant evaporative cooling cycle integrated with a ground source renewable energy for the pre-cooler process. Simulation results obtained using the TRNSYS software are compared with experimental data. The simulation of the mentioned systems are conducted in Bari (south of Italy), Palermo (south of Italy) and Ramsar (north of Iran) for the humid-mild climate of July. Assuming the low regeneration temperature (Treg) for the desiccant wheel is one of the highlights of this paper. Utilizing ground source heat exchanger (GSHE) will result in increase of the system potential in providing thermal comfort. The average thermal comfort achieves in Bari, Palermo and Ramsar in 95.72%, 93.94% and 93.15% of the time from 6 AM to 6 PM in July with utilizing the combination of GSHE and desiccant cooling system. The COP of this cycle is highly dependent on the Treg, and varies in the range of 0.35-0.53, 0.34-0.6 and 0.34-0.52 for the maximum Treg of 50 °C in Bari, Palermo and Ramsar, respectively.

Exergy Analysis of Fluidized Desiccant Cooling System.

One of the main challenges in the design and implementation of fluidized desiccant cooling (FDC) systems is increasing their low COP (coefficient of performance). Exergy analysis is one of the tools especially suitable for improvement and optimization of FDC systems. The improvement of performance is impossible as long as the main sources of exergy destruction are not identified and evaluated. In this paper, the exergy analysis was applied in order to identify these components and processes of the FDC system that are mainly responsible for exergy destruction. Moreover, the exergy efficiency of a simple fluidized desiccant cooler was determined. The results showed that fluidized beds and regenerative heat exchanger were the main exergy destruction sources with a 32% and 18% share of total exergy destruction, respectively. On the other hand, the direct evaporative cooler and air cooler placed after the desorbing fluidized bed were characterized by the lowest exergy efficiencies. This work contributes to better understanding of FDC operation principles and improvement of the performance of FDC technology.

Proposal and month-wise performance evaluation of a novel dual-mode evaporative cooler

Three climatic zones (composite, hot-dry, hot-humid) cover most of the regions in India. Direct evaporative cooler is suitable for dry and indirect regenerative evaporative cooler is suitable for humid months. To avoid the use of two different coolers for the same purpose during the composite climate (significant seasonal variations of temperature and humidity), a novel two-in-one evaporative cooler is proposed and numerically investigated in this study. Proposed cooler takes advantage of both types of evaporative cooler and be operated in dual mode: acts as direct evaporative cooler for hot-dry and acts as regenerative indirect evaporative cooler for hot-wet seasons. The working of both modes (direct and regenerative) is explained with the help of a diagram. Effects of channels height and water flow rate on cooling capacity, wet bulb effectiveness, and dew point effectiveness are discussed. The month-wise performance of the proposed cooler is evaluated for five Indian cities (Bhopal, Lucknow and Varanasi of composite climate; Ahmedabad of hot-dry climate; Kolkata of hot-humid climate). Suitability of the modes in hot months (April to September) and cities are evaluated with the help of a psychometric chart. Study reveals that the proposed cooler can be effectively and economically used for composite climate.

Numerical Simulations of Heat and Mass Transfer Process of a Direct Evaporative Cooler From a Porous Layer

This paper deals with the numerical study of the combined heat and mass exchanges in the process of direct evaporative cooler, from a porous media of laminar air flow between two parallel insulated walls. The numerical model implements momentum, energy, and mass conservation equations of humid air and water flow incorporating non-Darcian model in the porous region. The finite volume method is used for the mathematical model resolution, and the velocity–pressure coupling is treated with the SIMPLE algorithm. The main objective of this study is to examine the influences of ambient conditions and the porous medium properties (porosity and porous layer thickness) on the direct evaporative cooling performance from a porous layer. The major results of this study demonstrate that the porous evaporative wall could, in a satisfying manner, reduce the bulk air temperature. The better cooling performance can be achieved for lower air mass flow at the entrance and relative humidity. Additionally, the evaporative cooler is more effective for a high porosity and a thick porous medium, with an improvement achieving 23% for high porosity.

Thermal performance prediction of office buildings using direct evaporative cooling systems in the composite climate of India

This study predicts the thermal performance of office buildings using Direct Evaporative Cooling (DEC) systems for thermal comfort during the summer season of Indian composite climate. For this purpose, thermal monitoring of office buildings using DEC systems was carried out for peak summer months (April to July 2016) in Jaipur city. Experimental results were utilized to calibrate the thermal simulation models, developed using EnergyPlus. Taguchi design was further applied to develop L16 Orthogonal array of control factors and their respective levels for performing simulation runs. Simulation run outputs were then used for predicting supply air temperature and indoor air temperature as a function of independent variables (control factors) using Multiple Linear Regression technique. Statistical significance of temperature correlations was established using Analysis of Variance. Field validation from two other buildings (of similar characteristics) found a reasonably good agreement (R2 > 0.90) between the onsite measurements and the computed values of indoor temperature. The same methodology was also repeated to suggest mathematical correlations for specific humidity prediction of supply air and then indoor air. Finally, the potential of DEC to offset thermal discomfort was assessed using the proposed mathematical correlations. This was accomplished by plotting the predicted indoor conditions on Composite Climate-specific Adaptive Thermal Comfort Zone (CCATCZ) developed by the authors particularly for office buildings of Indian composite climate. Comfort prediction with ASHRAE Standard 55–2013 thermal comfort zone and CCATCZ revealed that approximately 42% and 52% of the thermal discomfort hours could be evaded with the use of DEC during the summer season.

Two Stage Evaporative Cooling of Residential Building Using Geothermal Energy

The weather of Iraq has longer summer season compared with other countries. The ambient temperature during this season reaches over 50 OC which makes the evaporative cooling system suitable for this climate. In present work, the two-stage evaporative cooling system is studied. The first stage is indirect evaporative cooling (IEC) represented by two heat exchangers with the groundwater flow rate (5 L/min). The second stage is direct evaporative cooling (DEC) which represents three pads with groundwater flow rates of (4.5 L/min). The experimental work was conducted in July, August, September, and October in Baghdad. Results showed that overall evaporative efficiency of the system (two coils with three pads each pad of 3cm) reach to 167 % with the temperature difference between ambient and supply is 26.2oC. While it reached 122.7% (one coil with three pads ) with the temperature difference between ambient and supply is 16OC and reduced to 84.88% and 84.36% for IEC and DEC respectively.