Faculty of Engineering, Mechanical Engineering
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Browsing Faculty of Engineering, Mechanical Engineering by Subject "AIR CONDITIONING"
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- item: Thesis-Full-textAnalysis of cooling tower performance of world trade center in Colombo(2020) Wickramasinghe W.A.D.P.; Perera KKCK; Manthilaka MMIDEnergy crisis first experienced in the world during 1975, since then it is ever rising phenomenon felt by every human being on earth. This is due to accelerated industrialization of the world and rapid growth of standard of living of people. Therefore, global Energy requirement is increased day by day deficit between energy available is increasing. It is felt that energy preservation is much more important than searching for New Sources. Sustainability has been introduced to building services to reduce waste of energy and provide for future. Green building concept is increasingly popular in terms of reducing fossil fuel usage and introducing alternative energy utilization. Reducing Carbon foot print of a building is the responsibility of the engineer in modern times to support the sustainability goals. Heating, Ventilating & Air conditioning (HVAC) systems in Commercial buildings accounts for 60% to 70% of their total power consumption. This thesis explores the possibilities of improving the configuration of cooling tower and optimization of the chiller plant. A central chiller plant for tall-building was analyzed for the effect of improving efficiency to enhance energy saving with varying cooling tower combinations and fan speed regulation. It was revealed that increasing the combination of cooling towers has a limitation of efficiency rise. However, reducing fan speed with increasing chiller combination prove to be success in the increasing efficiency of the chiller plant.
- item: Thesis-Full-textDynamic cooling load analysis on indoor thermal comfort state in passenger trains(2020) Kodituwakku TP; Manthilake, MMIDIncreasing passenger density makes indoor state of train compartments not thermally comfortable. Air conditioned train compartments have been introduced to provide comfortable pleasant interior environment to the passengers. However the trains consume in a high share of electricity for thermal comfort purposes thereby reducing their fuel economy and increasing emissions. Before adopting more air conditioned train compartments to the railway system, it is necessary to understand indoor thermal comfort state expected by passengers and the energy saving potential. This study discusses the acceptable indoor thermal comfort conditions and the variation in cooling load due to fluctuation of outdoor ambient conditions in moving train compartments. It was based on the Fangers thermal comfort model and a mathematical model was built to simulate this dynamic cooling load. Indoor thermal comfort parameters were examined by surveying of passengers travelled in air conditioned trains. The survey was conducted in trains run through the Colombo-Badulla main line and the northern line in Sri Lanka by interviewing 186 numbers of passengers using standard questionnaire. As independent variables, it was considered three main indoor thermal comfort parameters: temperature, relative humidity and air velocity. Analyzing the survey data using descriptive method, a comfort zone on psychometric chart was defined and accordingly indoor temperature and relative humidity of 26˚C & 55%RH were obtained as appropriate indoor thermal comfort parameters for railway passengers in Sri Lanka. On the other hand, energy saving potential was estimated through simulating dynamic cooling load values for the selected stations in both railway lines considered. Significant differences in dynamic cooling loads of train compartment were found between different stations and between different periods of time. The steady cooling load calculated according to the usual standard method was comparatively higher than the dynamic cooling load. Application of actual maximum dynamic cooling loads of a moving train compartment has been shown 10.9 kW & 5.9 kW of power reduction in train air condition system for mainline & northern line respectively. Thus the application of dynamic cooling load with reference to the time and space can lead to a significant energy saving in passenger trains.
- item: Thesis-Full-textStudy on Variable Refrigerant Volume Air-conditioning System(2015-10-16) Vitharana, SKP; Attalage, RADuring the last two decades, air-conditioning has become a basic requirement in industrial, commercial and residential sectors. With the widened use of air-conditioning in all the sectors, the human community has faced serious environmental and socio economic problems. Prevailing energy crisis and ever increasing energy pieces has made the situation worst. Under the scenario, various novel technologies have been emerged to the airconditioner market. Variable Refrigerant Volume (VRV) air-conditioning technology is also considered as an advanced technology developed to cater the need of efficient use of energy for air-conditioning. The major objective of the research study was to analyze the suitability of VRV airconditioning system, analyze the actual saving potential and cost effectiveness of VRV airconditioning system compared to the other available types of air-conditioning systems and access the maintainability of VRV air-conditioning system. The study was conducted at a selected representative installation namely at the Sovereign Residences of Central Bank of Sri Lanka. Summary of findings are as follows, • VRV air-conditioners are suitable for medium scale hotel applications. However, this conclusion cannot be generalized for all the installations and the appropriate air-conditioning system for particular building should be selected only after performing a comprehensive analysis of energy performance of considered options on that particular installation (preferably after a computer simulation and life cycle cost analysis of different options). Therefore, though the demand for VRV airconditioning system is prevailing due to the higher efficiency rating and the part load performance of the air-conditioning appliances, the desires of the purchases on energy saving potential of VRV air-conditioners could be satisfied only when it is selected for an appropriate application. • Saving potential of VRV air conditioners could be high as 18 % compared to the energy consumed by split air-conditioning systems when used for appropriate applications. Therefore, the VRV system can be considered as a potential candidate for the installations where the building occupancy and cooling load are regularly varying. Further, Chiller (Central) air-conditioning system can also be considered as a potential candidate as it performs almost efficiently as the VRV system. It consumes around 4 % more energy than VRV system. Study on VRV Air conditioning system Abstract v University of Moratuwa • Computer simulation (Equest) shown that VRV air-conditioning system is the most efficient option among the potentially applicable options considered for the building. However, the Life Cycle Cost (LCC) analysis shows that Chiller system is the most economical air-conditioning system for the same building. Therefore, it is vital to perform LCC analysis in addition to performance analysis when selecting the appropriate air-conditioning system for a building. • Maintainability of the VRV air-conditioning systems is acceptable. It is necessary to select the correct density and thickness of the refrigerant pipe insulation to minimize the possibilities of formation of condensation along the refrigerant pipes. Also, the power quality should be maintained at an acceptable level to ensure the durability and proper functionality of electronics of the VRV air conditioning equipment.
- item: Thesis-Full-textTechnological potential of small scale Ice thermal storage based air conditioning system in the generation phase for hotel & entertainment industry of Sri Lanka(2020) Godamunne RWSMS; Attalage RDemand for electricity during a day, varies with the time due to various factors. Electricity demand of Sri Lanka for a typical day could easily be divided into three main categories. One segment characterizes a very high sudden demand increase during later in the evening, and sharp decrease of the demand during the mid night until the next day early morning time and average daily demand during the day time. As a remedial action in facing this change of demand, electricity service providers generally encourage users to reduce the demand through different measures and also shift their consumption during the high demand period to the low demand period. This is achieved by introducing different electricity tariffs based on the time of the day. As Air Conditioning systems demand considerable percentage of building electricity consumption, Cold Thermal Storage technologies is an ideal candidate for electrical load shifting applications of buildings. This study explores the technological feasibilities and also reviews the engineering economics of building small scale Ice Thermal Storage based air conditioning system in the generation phase which has average capacity of 32 Ton Hours. The development of small scale thermal storage based air conditioning system is progressed through a detailed research work and final design was reviewed of its economic feasibility to be used for hotel rooms & 100 capacity movie theaters under Hotel & General electricity tariff structures respectively. This study further investigates in particular the ice building process in a water filled, limited length horizontal rectangular enclosure with the constant temperature glycol circulation system at the top & bottom surfaces. The rates of ice building on top and bottom surfaces were mathematically modeled based on the equations published by Et al. P. Bhargavi & Et al. Liang Yong. The dimensionless equations were then converted to dimensional and set of equations were derived to find the ice thickness Vs time, temperature profile along ice thickness at a given time and several other associated parameters necessary to calculate the heat transfer during water freezing. The goal was to find the maximum achievable ice thickness during 6.5 hours period and total energy extracted by the glycol circuit. Three glycol temperatures of -12C, -6C and -3C were considered and 3 data sets were built. By considering a given glycol temperature, the built ice thickness was calculated and tabulated for 6.5 hours period at 20 minutes intervals. Thereafter the temperature profile along the ice thickness was tabulated during the end of each 60 minutes (1 hour) up to 6 hours and final data set was tabulated at the end of 6.5 hours. Here the temperature profile was estimated at every 2.5 mm distance along the built ice thickness. The width & length of water filled rectangle enclosure was selected as 10 cm & 110 cm respectively and this unit is called Primary Ice Making Chamber. The height was selected based on the final built ice thickness which was decided based on temperature v of glycol circuit. Finally relevant total energy extracted and final ice volumes were calculated for 3 different glycol circuit temperatures. In order to achieve the uniform ice thickness inside the Primary Ice Making Chamber, counter flow arrangement was introduced to glycol circuits placed at top & bottom surfaces of it. Still there is a drop of final ice volume. The volume reduction was calculated and relevant total energy removed by the glycol circuit was calculated. This was repeated for 3 different glycol temperatures. The glycol circuits were designed and relevant flow rates were calculated to maintain the heat transfers for 3 designs scenarios. Finally 3 ice thermal storage designs were evaluated. The cost of manufacturing was calculated for all three designs. The operational cost was calculated for all three cases under hotel tariff for using at hotels and under general tariff for using at Movie Theaters. It was revealed that the price of chiller contributes to more than 50% of the cost of manufacturing for all 3 designs. The payback period for the use case of hotel rooms under hotel tariff was found to be 4.3 years. The use case of Movie Theater has a 3.4 years payback period. This clearly indicates the further possibility of reducing the payback period under both cases used by cutting down the capital cost of chillers. When these units are manufactured on an industrial scale, it would further reduce the cost of chillers by volume discounts. This study makes a clear indication that small scale ice thermal storage systems are economically feasible.