Investigation of sub-wet bulb temperature evaporative cooling system for cooling in buildings

The work presented in this thesis investigates design, computer modelling and testing a sub-wet bulb temperature evaporative cooling system for space air conditioning in buildings. The context of this evaporative cooling technology design is specifically targeted at locations with a hot and dry climate such as that prevailing in most regions of Middle East countries. The focus of this technology is to address the ever-escalating energy consumption in buildings for space cooling using mechanical vapour compression air conditioning systems. In this work, two evaporative cooling configurations both based on sub-wet bulb temperature principle have been studied. Furthermore, in these designs, it was sought to adopt porous ceramic materials as wet media for the evaporative cooler and as building element and use of heat pipes as heat transfer devices. In the first test rig, the prototype system uses porous ceramic materials as part of a functioning building wall element. Experimental and modelling results were obtained for ambient inlet air dry bulb temperature of 30 and 35oC, relative humidity ranging from 35% to 55% and intake air velocity less than 2 (m/s). It was found that the design achieved sub-wet bulb air temperature conditions and a maximum cooling capacity approaching 242 W/m2 of exposed ceramic material wet surface area. The wet bulb effectiveness of the system was higher than unity. The second design exploits the high thermal conductivity of heat pipes to be integrated as an effective heat transfer device with wet porous ceramic flat panels for evaporative cooling. The thermal performance of the prototype was presented and the computer model was validated using laboratory tests at temperatures of 30 and 35oC and relative humidity ranging from 35% to 55%. It was found that at airflow rates of 0.0031kg/s, inlet dry-bulb temperature of 35oC and relative humidity of 35%, the supply air could be cooled to below the inlet air wet bulb temperature and achieve a maximum cooling capacity of about 206 W/m2 of wet ceramic surface area. It was shown that the computer model and experimental tests are largely in good agreement. Finally, a brief case study on direct evaporative cooling thermal performance and environmental impact was conducted as part of a field trip study conducted on an existing large scale installation in Mina Valley, Saudi Arabia. It was found that the evaporative cooling systems used for space cooling in pilgrims’ accommodations and in train stations could reduce energy consumption by as much as 75% and cut carbon dioxide emission by 78% compared to traditional vapour compression systems. This demonstrates strongly that in a region with a hot and dry climate such as Mina Valley, evaporative cooling systems can be an environmentally friendly and energy-efficient cooling system compared to conventional vapour compression systems

Investigation of sub-wet bulb temperature evaporative cooling system for cooling in buildings

The work presented in this thesis investigates design, computer modelling and testing a sub-wet bulb temperature evaporative cooling system for space air conditioning in buildings. The context of this evaporative cooling technology design is specifically targeted at locations with a hot and dry climate such as that prevailing in most regions of Middle East countries. The focus of this technology is to address the ever-escalating energy consumption in buildings for space cooling using mechanical vapour compression air conditioning systems. In this work, two evaporative cooling configurations both based on sub-wet bulb temperature principle have been studied. Furthermore, in these designs, it was sought to adopt porous ceramic materials as wet media for the evaporative cooler and as building element and use of heat pipes as heat transfer devices. In the first test rig, the prototype system uses porous ceramic materials as part of a functioning building wall element. Experimental and modelling results were obtained for ambient inlet air dry bulb temperature of 30 and 35oC, relative humidity ranging from 35% to 55% and intake air velocity less than 2 (m/s). It was found that the design achieved sub-wet bulb air temperature conditions and a maximum cooling capacity approaching 242 W/m2 of exposed ceramic material wet surface area. The wet bulb effectiveness of the system was higher than unity. The second design exploits the high thermal conductivity of heat pipes to be integrated as an effective heat transfer device with wet porous ceramic flat panels for evaporative cooling. The thermal performance of the prototype was presented and the computer model was validated using laboratory tests at temperatures of 30 and 35oC and relative humidity ranging from 35% to 55%. It was found that at airflow rates of 0.0031kg/s, inlet dry-bulb temperature of 35oC and relative humidity of 35%, the supply air could be cooled to below the inlet air wet bulb temperature and achieve a maximum cooling capacity of about 206 W/m2 of wet ceramic surface area. It was shown that the computer model and experimental tests are largely in good agreement. Finally, a brief case study on direct evaporative cooling thermal performance and environmental impact was conducted as part of a field trip study conducted on an existing large scale installation in Mina Valley, Saudi Arabia. It was found that the evaporative cooling systems used for space cooling in pilgrims’ accommodations and in train stations could reduce energy consumption by as much as 75% and cut carbon dioxide emission by 78% compared to traditional vapour compression systems. This demonstrates strongly that in a region with a hot and dry climate such as Mina Valley, evaporative cooling systems can be an environmentally friendly and energy-efficient cooling system compared to conventional vapour compression systems

Investigation of a super performance dew point air cooler and its application in buildings

Based on extensive literature reviews, technical opportunities were identified to improve the energy efficiency of a dew point air cooler. This applied research aimed to develop a super-performance dew point air cooler to replace or partly replace the conventional energy-intensive air conditioners applicable to buildings.This research followed the methodology of combined theoretical and experimental investigation and a procedure of concept formation, validating and updating. A simulation software was developed and validated to investigate the impacts of the geometric configuration and operational conditions on the unit’s cooling performance and assist the prototype design. As a result, a novel dew point air cooler prototype, featuring innovative structure of the heat and mass exchanger, application of new materials and new processes, unique water distribution and control scheme and exclusive self-developed simulation software, was constructed and tested under controlled laboratory environment. Two patents were generated, one of which has been authorized by the China State Intellectual Property Office and the other has been filed in the Intellectual Property Office of the United Kingdom.Under standard testing conditions, i.e. dry-bulb temperature of 37.8oC and the coincident wet-bulb temperature of 21.1oC, the prototype cooler achieved a wet-bulb cooling effectiveness of 114% and dew-point cooling effectiveness of 75%, yielding a significantly high Coefficient of Performance (COP) of 52.5 at the optimal working air ratio of 0.364. The performance testing was also carried out under various simulated conditions representing the climates of hot & dry, warm & dry, moderate, warm & humid and the wet-bulb effectiveness of the prototype kept in the range 112% to 128% and dew-point effectiveness of 67%-76%, giving a COP of 37.4-52.5. Compared to the conventional vapour compression air conditioners which have a COP of around 3, the prototype cooler had 11-17 times higher COP, leading to a reduction in electrical power consumption by around 92% to 94%.A dedicated case study of the proposed dew point cooler based on conditions in Beijing, a representative city in warm and humid climate, was carried out to predict the annual operational performance, economic rewards, and associated environmental benefits. Compared to the conventional packaged air conditioners, 91.4% of annual power demand could be saved. The annual water consumption is less than 0.3 tonnes to provide the cooling of 2428.1 kWh. And the payback period of static investments would be less than 4 years to replace an equivalent packaged air conditioner.A significant leap forward has been achieved with this study and this is expected to open enormous global business in the very near future, thus bringing about great economic, environmental and sustainability benefits worldwide

Energy Systems and Applications in Agriculture

Agriculture, as a production-oriented sector, entails energy as a substantial input by which global food security is ensured. Agricultural systems require energy for farm machinery and equipment; lighting; heating, ventilation, and air-conditioning (HVAC); food processing and preservation; fertilizer and chemical production; and water/wastewater treatment/application. Increasing agriculture mechanization mitigates conventional energy reserves that escalate greenhouse gas emissions and climate change.This book aims to offer energy-efficient and/or environment-friendly ways for the agriculture sector to achieve the 2030 UN Sustainable Development Goals. The book provides cutting-edge research on next-generation agricultural technologies and applications to develop a sustainable solution for modern greenhouses, temperature/humidity control in agriculture, farm storage and drying, crop water requirements, agricultural built environment, and wastewater treatment

A multi-stage membrane system for cooling and water recovery in horticultural greenhouses

The increasing issues of water scarcity and food insecurity highlight the necessity to utilise water and produce food more efficiently. Agriculture, which accounts for 70% of global water usage, is related to both these issues. Controlled-environmental greenhouses have been investigated as a potential solution, with liquid desiccant air-conditioning showing promising results. However, controlled-environmental greenhouses face challenges in hot climates. This is because conventional liquid desiccant air-conditioning utilises thermal energy-intensive liquid desiccant regenerators, highlighting the need for an alternative regenerator with lower energy requirements. Thus, a comparison of six membrane-based desalination technologies was conducted, and multi-stage nanofiltration was identified as the most promising for use as a liquid desiccant regenerator (Chapters 1 and 2). After conducting a steady-state investigation on multi-stage nanofiltration regeneration combined with liquid desiccant air-conditioning for greenhouse applications, it was found that the proposed system could achieve better indoor conditions for crops compared to thermal regenerators and conventional cooling technologies (Chapter 3). Consequently, the practical feasibility of nanofiltration regeneration was demonstrated through dead-end filtration experiments using a 1-stage regenerator (Chapter 4) and cross-flow filtration experiments using a 2-stage regenerator (Chapter 5). Additionally, a 2-stage regenerator model was developed and verified with errors below 11% compared to the experimental data (Chapter 5). The verified model was then applied to a dynamic simulation of a greenhouse using the proposed system (Chapter 6). The proposed system enables year-round cultivation and saves 50% of water in desert and semi-arid climates where crop production is challenging, and 30% in tropical climates where agriculture typically overuses water. By reducing water demand and enabling year-round cultivation, the proposed system addresses the issues of water scarcity and food insecurity in hot climates

Energy: A continuing bibliography with indexes, issue 13

This bibliography lists 1036 reports, articles, and other documents introduced into the NASA scientific and technical information system from January 1, 1977 through March 31, 1977

Proceedings of the 9th Arab Society for Computer Aided Architectural Design (ASCAAD) international conference 2021 (ASCAAD 2021): architecture in the age of disruptive technologies: transformation and challenges.

The ASCAAD 2021 conference theme is Architecture in the age of disruptive technologies: transformation and challenges. The theme addresses the gradual shift in computational design from prototypical morphogenetic-centered associations in the architectural discourse. This imminent shift of focus is increasingly stirring a debate in the architectural community and is provoking a much needed critical questioning of the role of computation in architecture as a sole embodiment and enactment of technical dimensions, into one that rather deliberately pursues and embraces the humanities as an ultimate aspiration

Indoor air Quality and Its Effects on Health in Urban Houses of Indonesia: A case study of Surabaya

There is a possibility that the sick building syndrome has already spread widely among the newly constructed apartments in major cities of Indonesia. This study investigates the current conditions of indoor air quality, focusing especially on formaldehyde and TVOC, and their effects on health among occupants in the urban houses located in the city of Surabaya. A total of 471 respondents were interviewed and 82 rooms were measured from September 2017 to January 2018. The results indicated that around 50% of the respondents in the apartments showed some degrees of chemical sensitivity risk. More than 60% of the measured formaldehyde levels in the apartments exceeded the WHO standard, 0.08 ppm. The respondents living in rooms with higher mean formaldehyde values tended to have higher multiple chemical sensitivity risk scores. KEYWORDS: Indoor air quality, Sick building syndrome, QEESI, Formaldehyde, Developing countrie

Advancing Green Building Rating Systems Using Life-Cycle Assessment

The aim of this research was to quantitatively analyze the potential ability of life cycle assessment (LCA) in combination with green building rating systems (GBRS), such as Leadership in Energy and Environmental Design (LEED), to reduce a building’s environmental impacts, considering variations in climate, renewables, energy sources and economic aspects. First, international variations in the energy use and associated environmental life cycle impacts were investigated. A reference Building Information Model (BIM) office building was developed and placed in 400 locations with changes to meet energy standards. LCA was then performed on all the buildings’ energy consumption. The results varied considerably between the U.S. (394 ton CO2 eq) and international (911 ton CO2 eq) locations. Since GBRS are expanding internationally, energy source considerations for buildings should be considered with a particular suggestion of targeted goals reductions versus aggregated certifications. Second, the BIM and LCA models were extended to include on-site renewable energy (wind and solar) and located in 25 locations around the world. An LCA and LCCA were performed to consider different energy sources including renewables and associated prices at each site. Environmental impacts and economics varied dramatically. The requirements of renewable energy generation in existing GBRS need to be developed and changed to be a percentage of what is actually available on-site, instead of a fixed percentage of the building’s energy. Third, a comparative analysis was conducted for three whole-building LCA tools available today. The software tools vary in key aspects such as intended users, design stage, and time. One of the most important challenges is a comparison with a baseline. The results indicate that given the same building, the LCA results varied by about 10% in the pre-occupancy impact to 17% in the operational impact. This reinforces the need to not only refine LCA methods for GBRS, but also work towards robust data sets for building systems and products. At a minimum, GBRS should include LCA uncertainty analysis into their systems