Browsing by Author "Wijewardane, MA"

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item: Conference-Abstract
Analysis of the heat column formation in a 10 storey building
Prasath, K; Thavanees, S; Prakalathan, A; Ranasinghe, RACP; Wijewardane, MA
This paper aims to analyse the formation of heat column and its effects on the performance of the air conditioning systems. The computational fluid dynamic techniques combined with experimental validation were used to investigate the temperature distribution along the heat column under different loading conditions. Further the influence of wind and the humidity were also predicted. Results show that a significant loss of performance of the AC system can be expected under the influence of the heat column.
item: Conference-Full-text
An analytical approach for designing turbo expanders for organic rankine cycle
(IEEE, 2022-07) Ratnayake, RMSA; Bandara, RMAT; Sandaruwan, PHPL; Wijewardane, MA; Ranasinghe, RACP; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
ORCs (Organic Rankine Cycles) are becoming widely attractive for waste heat use since they facilitate power generation from low thermal content supplies. ORC may be optimized in various ways after determining the appropriate operating working fluid and design parameters. This article introduces a new design approach to produce a turbo expander demonstrated for a 1kW ORC utilizing R245fa as the working fluid. The obtained initial dimensions of the rotor were evaluated using performance criteria commonly used in turbo-machinery designing and the best results were selected after conducting several iterations. The inlet tip speed U 5 is considered as the primary design variable since it is restricted by mechanical stress considerations. The results obtained from the rotor analytical study are then utilized for stator, volute, and diffuser designs.
item: Conference-Full-text
Applicability of phase change materials (PCMS) for peak load shifting of air conditioning and mechanical ventilation (ACMV) systems of office buildings in tropical climates
(Ceylon Institute of Builders, 2017-06) Wijewardane, MA; Figurado, SA; Kajaharan, M; Weerasinghe, NDAM; Ranasinghe, RACP; Sandanayake, YG; Ramachandra, T; Gunatilake, S
Air Conditioning and Mechanical Ventilation (ACMV) Systems are often used to maintain the thermal comfort and the indoor air quality in office buildings in tropical climates. These ACMVs usually account for more than 50% of the total energy consumption of the buildings. Compared to other available technologies, use of Phase Change Materials (PCMs) has been identified as an attractive innovative technology to reduce the peak cooling load and also to shift the peak cooling load to after office-hours. Temperature of building envelopes constructed using conventional materials such as bricks and concrete tend to vary with the surrounding environmental conditions, as they only absorb or release the sensible heat. On the contrary, PCMs can absorb or release much larger amount of thermal energy from/to the surrounding as latent heat, while maintaining the building envelope temperature unaffected under varying environmental conditions. Thus, conventional building envelopes accompanied with PCMs are able to significantly reduce the external heat gains into the conditioned spaces of the buildings, resulting a significant reduction in the peak cooling load. This study is mainly focused on exploring the applicability of PCMs for hot and humid tropical climates. Numerical analysis supported and validated by an experimental program and a case study revealed that by covering exterior of building envelop with 5 mm - 10 mm thick PCMs can reduce the building peak cooling load by 8% - 12%. Moreover, it was found that the peak cooling load could be easily shifted to after office hours by increasing the PCM thickness. Economic analysis showed that the PCMs with higher thermal cycles reduces the pay back periods up to 2 - 3 years and, further supported the use of low-temperature PCMs for building applications. Findings of this study recommend to incorporate the PCMs on the building envelops of the sunlit walls to reduce the peak cooling load of the building with the aim of reducing the energy consumption by the ACMV system.
item: Conference-Full-text
Benchmarking energy and water consumption of supermarkets in Sri Lanka
(IEEE, 2022-07) Senanayake, SMCP; Wijewardane, MA; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
Buildings are responsible for about 40% of global energy consumption, 42% of global CO 2 emissions and about 30% of global fresh water consumption. Therefore, the importance of energy and water consumption benchmarking in buildings has become a major objective for governments and relevant authorities, in order to reduce the energy and water consumption by the buildings. Energy consumption benchmarks for commercial sector, hospitality industry, apparel industry and tea processing industry have been already developed and are available for Sri Lanka. However, electricity and water consumption benchmarking for retail supermarkets have not been established yet. Therefore, during this study, electricity and water consumption benchmarking for Sri Lankan retail supermarkets were estimated and proposed. According to the analysis, electricity consumption benchmarks were obtained as 780.0 kwh/year/m 2 per sales floor area and 465.4 kwh/year/m 2 per total floor area. Moreover, mean specific electricity costs were obtained as 19,465.90 Rs/year/m 2 per sales floor area and 11,621.20 Rs/year/m 2 per total floor area, provided that electricity cost is calculated per GP 2 tariff structure of Ceylon electricity board. In addition, water consumption benchmarks were obtained as 246.5 L/year/m 2 per sales floor area and 137.2 L/year/m 2 per total floor area. Moreover, a building energy simulation model was developed using eQUEST simulation software, to obtain the specific electricity consumption and average annual electricity consumption breakdown of the retail supermarkets. Eventually, the results obtained from the simulation model were validated against the results obtained from the numerical model, and then compared and verified with the international benchmarks established for retail supermarkets.
item: Article-Full-text
Comprehensive analysis of thermoelectric generation systems for automotive applications
(Elsevier, 2017) Stobart, R; Wijewardane, MA; Yang, Z
With the introduction of carbon dioxide emissions legislation for vehicles, the pressure on fuel efficiency in vehicle propulsion systems has grown significantly. Cost-effective efficiency improvements have become the topic of intensive research efforts. Amongst such efficiency measures, waste heat recovery (WHR) has attracted a deep interest both in the industrial and academic sectors. As a potentially low maintenance solid-state implementation, the thermo-electric generator (TEG) represents a promising candidate technology. Thermoelectric (TE) solutions, compared with other WHR methods have an appealing simplicity that could translate rapidly into robust engineering solutions. Achieving competitive efficiencies and low manufacturing cost however remains a substantial research challenge. Critical to progress are modelling processes that allow solutions to be formulated and assessed. The work reported in this paper demonstrates that a modelling process that makes use of mainstream computational fluid dynamics (CFD) codes is feasible. A benchmark TEG design first simulated and then run on an engine test bed showed agreement between simulation and experiment to within 10%. Closed form results for the optimised performance of module and overall TEG design have been reported in the literature and lend important insights into implementation methods. However practical implementation must take account of varying conditions and spatial variations in the heat exchange process. A CFD code that would permit a detailed evaluation TEG parameters and material properties has been demonstrated with a plate-fin design of heat exchanger. Meanwhile a simpler model has achieved agreement to within 12% with the CFD code indicating that a rapid modelling process is feasible and could support new “in the loop” test techniques.
item: Conference-Full-text
Computational analysis on the influence of design parameters and ambient conditions on performance of single stage traveling wave thermoacoustic generator
(IEEE, 2023-12-09) Wickramasinghe, MDA; Manthilake, MMID; Wijewardane, MA; Ranasinghe, RACP; Abeysooriya, R; Adikariwattage, V; Hemachandra, K
The demand for clean and sustainable energy, energy conservation and recovery has increased with the growth of population and adverse impacts on the environment caused by using conventional energy sources. By transforming waste heat into sound, thermoacoustic technology is utilized to recover energy. Around the world, more study is being done in this area. Out of the two technologies used for thermoacoustic energy conversion, use of traveling waves was found to be more efficient than using standing waves. However still, the correlations between energy conversion efficiency and the design parameters need to be established by simulation as well as experiments. Here, a single stage traveling wave thermoacoustic generator was considered using an existing computational model. The influence of the ambient temperature and the length of the regenerator on the energy conversion efficiency was investigated. According to the results, the efficiency of the device increases with increasing ambient temperature for a constant regenerator length, while for a given ambient temperature the efficiency increased with the increasing regenerator length. There is a limit to this rise of efficiency with the regenerator length and after which, the acoustic behavior appears to be nonexistent. Further studies on this are being carried out.
item: Thesis-Abstract
Condensate recovery from air handling units and fan coil units to reduce the water consumption by the air conditioning systems
(2023) Ragulakeethan, S; Wijewardane, MA; Lekamwasam, S
This study investigates the potential for reduction of makeup water consumption by recovering condensate captured from Air Handling Units (AHUs) and Fan Coil Units (FCUs) of central chilled water system in hot and humid climatic conditions. In conventional air conditioning systems, significant amounts of condensate is generated at different components and typically discharged as waste. The cooling towers are used to enhance the heat rejection efficiency of the condenser of the chilled water systems. Usually, it requires a significant amount of makeup water (2% of nominal flow rate) to replenish the regular water losses, mainly due to the evaporation. Therefore, the condensate collected from the AHUs and FCUs can be routed through the cooling tower, resulting in the reduction of potable water usage and to improve the quality of the cooling tower water. This paper presents a method to collect the condensate water and store it in a holding tank for later use in offsetting the cooling tower makeup water requirement. The analysis was performed by collecting the condensate from AHUs/FCUs of five different types of buildings in three different weather zones in Sri Lanka with varying climatic conditions. The findings demonstrate that condensate recovery can be an effective strategy to reduce the water consumption in central air conditioning systems, especially in regions facing water scarcity or high-water costs. The potential benefits of this approach include decreased water consumption, lower water bills, and a reduced environmental impact and eventually the overall energy consumption of the system. Keywords: Water conservation, Hot and humid climate, Condensate recovery, Makeup water, Central air conditioning system
item: Conference-Abstract
Design, fabrication and testing of a thermo-electric refrigeration unit
(2008) Fernando, SVA; Wijesekara, RGRP; Wijewardane, MA; Watugala, GK; Attalage, RA
A Thermo-Electric Refrigeration Unit to be used as a portable vaccine cooler in rural areas, where the main grid supply is unavailable was designed and constructed. Thermo-Electric modules working on the Peltier Effect, which causes to generate hot and cold sources when a current passes through dissimilar semiconductor materials, have been employed. The cold source is used to cool the refrigerating environment within its cabin and heat of the hot source is evacuated to the surrounding environment. The designed refrigerator is smaller in size and light in weight. The input power to the refrigerator is around 90 W. Minimum designed temperature is 15 oc less than the ambient temperature which is suitable for vaccine preservation. The cooling volume of the refrigerator is 18 liters.
item: Conference-Full-text
Establishing the relationship between indoor and outdoor temperature of an existing office building using hybrid physics based and data driven models
(IEEE, 2022-07) Serasinghe, SVIRV; Nissanka, ID; Wijewardane, MA; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
Building cooling energy demand accounts for a significant fraction of the global energy demand. This is significant in hot and humid countries especially in the South Asian region where the electricity infrastructures are at risk due to increasing demand for building cooling due to various factors such as global warming and growth of population. Although this risk has been identified, limited research has been conducted in energy demand predictions in these climatic zones. Nevertheless, the use of data driven modelling for demand predictions of buildings is becoming popular around the world. Hence, this paper focuses on developing a model to predict indoor temperature from outdoor conditions to estimate the cooling energy demand. The model presented is a hybrid model which is a combination of physics based and data driven models. The model was trained and validated for an existing office building in a tropical climate zone. Model parameters were calculated using different surveys. The developed model has been used to calculate the cooling energy demand of the selected zones. It was observed that the demand increase is dependent on various zone envelope properties (window area, floor area etc.) and these zones show a significant correlation between indoor and outdoor conditions.
item: Conference-Full-text
Estimation of embedded energy of some selected vegetables in the vegetable value chain, Sri Lanka
(IEEE, 2022-07) Dasanayake, DMCMK; Wijewardane, MA; Jayasinghe, CVL; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
Vegetable value chain is an energy intensive process. Embedded energy of the vegetables from farm to the retailer market has a significant impact on the market prices of the vegetables. However, the market price of the vegetable does not directly depend on the embedded energy cost of a particular vegetable as the availability of vegetables in the market varies depending on the different harvesting seasons in the calendar year. Sri Lanka is an agricultural country which is self-sustain for its total vegetable requirement. This study explains the estimation of embedded energy of some selected vegetables in the vegetable value chain of Sri Lanka.
item: Conference-Full-text
Identify the differences of ac load requirement with respect to the floor number in high rise buildings
(IEEE, 2018-05) Madhusanka, CKI; Ranatunga, RGSM; Thilakarathna, EGDR; Ranasinghe, RACP; Wijewardane, MA; Chathuranga, D
Urban Heat Island phenomenon and heat column formation effects are directly affected by the outdoor temperature of the building. This leads to high on-coil temperature at the outdoor unit of the air conditioners (ACs). As a result, energy consumption by the AC system increases and Coefficient of Performance decreases and eventually provides low AC capacities than the rated amounts by the manufacturer. In reality and very often, building designers and shop keepers decide the required AC capacity for a given space referring the already tabulated cooling load capacity per unit area without performing any cooling load calculation or considering the other factors that would affect to the AC load. When it comes to high rise buildings, their approximations are often incorrect and obtaining the required thermal comfort from low capacity machineries is impossible. In order to prevent under-estimation of the required AC load, this study investigated the temperature increment of the outdoor conditions due to UHI and heat column formation by conducting few case studies and with the support of the Computational Fluid Dynamics simulations. It was revealed that in high-rise buildings surrounding temperature generally increases by 1.0 - 1.7oC for a 10-story building and the cooling load requirement of 10th floor in a high-rise building increases by 9-10% with respect to the ground floor.
item: Conference-Extended-Abstract
Investigation on the effect of different channel geometries of thermal wheel for energy transfer efficiency
(2021-09-06) Polgolla, AMCK; Herath, HMDP; Wickramasinghe, MDA; Wijewardane, MA; Ranasinghe, RACP
Inside buildings, heating, ventilation, and air conditioning systems are utilized to provide a comfortable environment. However, they account for a significant percentage of overall total energy consumption: in the United States, they account for about 50% of building final energy consumption and 20% of total energy consumption. [1]. The installation of a heat exchanger between the exhaust and fresh air streams is critical, owing to the significant energy savings. [2], [3]. Thermal wheels have recently gotten a lot of attention because of their high efficiency and low-pressure loss when compared to other energy recovery solutions [4]. The goal of this research is to give a comprehensive study and optimization of Thermal wheel design, with the goal of enhancing sensible effectiveness while reducing pressure loss based on channel shape.
item: Thesis-Full-text
Low grade thermal energy harvesting from thermo-acoustic generator
Rathnayake, RKA; Manthilaka, MMID; Wijewardane, MA
A thermoacoustic generator is an energy conversion device. It converts thermal energy into acoustic energy by using the stack. That is porous medium that contains a large number of channels. The acoustic energy can be converted into electric energy by the alternator. The condenser mics, speakers and piezoelectric materials can use as alternators. The atmospheric air is used as a working fluid. Generally, Helium, Neon, Argon and their proper mixtures are preferred as the working fluid. That has a high sound speed and high mean pressure. That types of working fluids yield high acoustic power density. prime mover. Thermoacoustic generator is an environmental friendly. Its biggest advantage is that they do not use harmful gas as a working fluid. It uses helium which is noncombustible, nonpoisonous inert gas having zero global warming effect. The generator length is quarter wave length that is equal to the length of a resonator tube. The alternator and the stack are fixed inside the resonator tube. The solar thermal energy, waste heat from internal engine and heat from industrial waste are used as a hot heat exchanger (heat source). The cold heat exchanger (sink) is water or atmospheric air. The thermoacoustic generator has two heat exchangers they produce temperature difference across the stack. Now acoustic pressure wave creates and it propagates through a resonator tube. The pressure wave can work on the alternator. That does not contain any moving parts (no lubricant) and decrease the maintenance cost. The only disadvantage of this thermoacoustic engine is low efficiency. Lots of researches are developing on the stack and resonator design. It is based on linear thermoacoustic theory combined with numerical simulations in the thermoacoustic design soft wares. The 612 mm long thermo-acoustic generator was design, built and tested. That device generates sound at 84.2℃ -275.7℃ temperature difference across the stack. Approximately, device produced acoustic power and internal efficiencies of the acoustic generator are 0.90-19.20 W and 0.05-0.06 % respectively.
item: Article-Full-text
Numerical model-based prediction of performance of single stage traveling wave thermo-acoustic engines
(Elsevier, 2021) Herath, HMDP; Wijewardane, MA; Ranasinghe, RACP
In the recent past, attraction towards the new power generation technologies and thermal energy recovery have become exponentially increasing due to the environmental and economic concerns. Thermo-acoustic generation has been identified as an attractive novel technology for low-grade energy recovery and power generation. Only moving component of the thermo-acoustic generation system is the linear alternator, which is used to convert acoustic energy into electrical energy, and hence, it leads to increase the reliability of thermo-acoustic systems with comparative to the other power generation technologies. Traveling wave thermo-acoustic generators have higher efficiencies with respective to its counterpart, standing-wave thermo-acoustic generators. Traveling wave thermo-acoustic generators are much economical and less complex as it can be operated with ambient air at atmospheric pressure conditions as the working fluid. During this study, a single stage traveling-wave thermo-acoustic engine was modeled and validated using available test results in the literature. The validated model was used to predict the optimum working conditions for a traveling wave thermo-acoustic engine to obtain the maximum efficiency from the engine. Results show that the increment of temperature in hot heat exchanger tends to increase the efficiency of the system.
item: Conference-Full-text
Reducing the excess energy consumption on higher ventilation flowrates to control the co2 levels of the central air conditioning systems in polluted urban areas by co2 capturing
(IEEE, 2022-07) Wijewardane, MA; Herath, HMPD; Ranasinghe, RACP; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
Controlling the air quality of the indoor environment is extremely important to improve the health and the productivity of the occupants. The air quality is maintained by providing ventilation air following the ASHRAE standards. The ventilation air (outdoor fresh air), usually processes in the Air Handling Unit (AHU) of the Central AC system, and delivers to the occupant zones. However, supplying outdoor air with increased levels of CO 2 will adversely affect for the health and the productivity of the occupants. In this study, it was found that the CO 2 levels in the indoor environments increase with the increased atmospheric CO 2 levels and the recirculation air percentage. When the CO 2 level of the outdoor air is higher, IAQ can only be controlled by supplying more fresh air to the indoor environment. However, it increases the load on the Cooling Coil and eventually, electricity consumption of the chiller increases. Moreover, the higher excess air flowrates of the MVAC systems require larger fans and increased equipment costs. Therefore, it has been suggested that a CO 2 Capturing Device which is suitable for MVAC systems can handle these extreme scenarios and reduce the operating and maintenance cost of the MVAC systems.
item: Conference-Full-text
Use of under floor air distribution (ufad) system for energy saving assessment
(IEEE, 2023-12-09) Jeewakanthi, AGS; Ranasinghe, RACP; Wijewardane, MA; Abeysooriya, R; Adikariwattage, V; Hemachandra, K
Heating Ventilation and Air Conditioning (HVAC) systems are used to maintain the thermal comfort and indoor air quality (IAQ) of an indoor environment. With the recent experience of contagious fatal air borne viruses, the requirement of controlling the IAQ of buildings has become utmost important. HVAC systems of buildings in hot and humid climates are responsible for 50%-60% of the total building energy consumption. Air distribution system supplies the processed air to the occupancy zones and exhausts the return air. There are three main air distribution systems and are: conventional Overhead Air Distribution (OHAD) systems, Traditional Displacement Ventilation (TDV) systems and Underfloor Air Distribution (UFAD) Systems. Although the UFAD systems have many advantages over the conventional systems according to the configuration, UFADs had not been adopted in to practice due to lack of research investigations to convince the clients, designers and contractors to incorporate and install these systems in buildings. Therefore, this paper investigates the temperature distribution, air speed variation, Draught Rate (DR), Percentage of Dissatisfied (PD) and temperature effectiveness characteristics of UFAD systems from a validated Computation Fluid Dynamics (CFD) model. CFD results proved that the thermal comfort and localized energy performance of UFAD systems are higher than that of the conventional TDV systems.
item: Article-Full-text
Working fluid selection of Organic Rankine Cycles
(Elsevier, 2020) Herath, HMDP; Wijewardane, MA; Ranasinghe, RACP; Jayasekera, JGAS
Organic Rankine Cycles (ORCs) are identified as one of the best candidates to generate electricity from low-grade heat sources. ORCs operate on low temperatures and low pressures with comparative to conventional Rankine Cycles. Therefore, organic fluids or refrigerants can be used as the working fluids for ORC applications, instead of water, which is more suitable for high-pressure and high-temperature applications. The performance and the system design of the ORC system are entirely dependent on the working fluid, and hence, working fluid selection for ORCs is utmost important for a particular application, i.e. solar thermal, geothermal or waste heat recovery. Performance of the ORCs for seven (07) working fluids: R-134a, R-245fa, Benzene, Methanol, Ethanol, Acetone and Propane (R-290) have been studied during this work. Results of the study show that Benzene and Methanol based ORC systems perform more efficiently with comparative to the other working fluids considered in the analysis and, they require lower fluid mass flowrates per unit of power generation relative to other fluids used in the analysis.