Browsing by Author "Ranasinghe, C"

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item: Article-Full-text
An assessment on the test setups used for energy labeling of ceiling fans
(Springier, 2021) Casseer, DR; Ranasinghe, C
Ceiling fans are used all over the world as a mean of enhancing indoor thermal comfort. A number of grading programs have been initiated for assessing energy performance of ceiling fans, such as ANSI/AMCA 230, Energy Star, IEC 60879, IS 374 and SLS 1600. The configurations of test setups used for performance evaluations in these standards have significant differences to each other. In this study, the influence of such differences on the calculated performance grade of ceiling fans were investigated and the suitability of each dimension of the test set-up is discussed. Particular emphasis was placed on quantifying the effect of the cylindrical drum used in Energy Star and SLS test methods. For this assessment, extensive three-dimensional numerical simulations and experimental measurements were used. Accordingly, the effect of cylinder height, gap between the fan rotation plane and the cylinder, cylinder diameter and the dimensions of the test chamber were investigated. Results show that, the test cylinder, has no significant impact on the calculated performance grade of the tested ceiling fan (variation is less than 2%), and may be eliminated from the test setup. This justifies the recent decision of AMCA on the removal of test cylinder from the fan test set-up. Further, it was also found that the set up dimensions considered herein is large enough so that the calculated start rating is uneffaced by the surrounding solid walls.
item: Thesis-Abstract
Benchmarking water demand of low-income housing apartment complexes in Colombo, Sri Lanka
(2024) Gallage, SL; Ranasinghe, C; Jayasundara, R; Wijewardane, A
Along the main roads, Sri Lanka's coastline regions are fast urbanizing and expanding. The progress of these development works increased the population inside the urban areas, which created new social and economic issues. The high-density apartment complexes as high-rise apartment buildings are introduced to mitigate these social and economic issues. To maintain sustainable development in these urban areas, providing essential facilities for these apartment buildings is important. 70,000 low-cost housing units were scheduled for construction as part of the Urban Regeneration program and Sri Lanka's National Physical Plan (2011-2030). These plan to relocate the people currently residing in underserved areas of Colombo city. Providing the essential facilities for these apartments does not assure the sustainability of the development. Overuse and waste are also required to be minimized, and optimum usage of these facilities is also to be assured. As a result, efficient buildings that preserve the environment are necessary for sustainable development, and these services need to be standardized. There are building rating systems like LEED, BREEAM, and Green Star that are well recognized in this context. In Sri Lanka, the Green Building Rating system, UDA Green, is recognized to describe a building's efficiency. Energy efficiency is what these rating systems are primarily concerned with. Concerns about water efficiency are also significant in this context because Sri Lankan water demand benchmarks are not established, which makes it difficult for construction designers to create effective solutions for these structures and monitor the efficiency of the existing apartment buildings. The study of establishing a benchmark for the water demand of low-income housing apartments requires studying of socio-economic behaviour of this community. A survey questionnaire was used to collect the information required for this study from 500 randomly chosen sample residents spread over 18 low-income apartment complexes in the Colombo area. A benchmark for the water demand in apartment buildings for low-income housing was developed after the survey's results were analysed. The benchmark water demand values for low-income housing are 170.16 litres per person per day and 850 litres per apartment per day. Keywords: Water demand benchmarking, Low-Income housing apartments, socio-economic behaviour, Survey questionnaire
item: Thesis-Full-text
Comparison of biomass cookstoves in Sri Lanka
Chandrasena, RIK; Ranasinghe, C
Biomass plays an important role in Sri Lanka Energy Sector. The consumption of biomass in the commercial and household sector is declining due the popularity of fossil fuels. Consumption of biomass is getting less popular due to various reasons. Handling difficulties due to various sizes, combustion difficulties due to various calorific values, low combustion efficiency due to high moisture content transportation cost due to bulk size and moisture. To evaluate the performance ofselected biomass cookstoves thermal efficiency together with other performance parameters were tested by Shell Foundation Version 4.3.2 Water Boiling Test. The tested stoves are Semi-enclosed firewood cookstove, popular Anagi-2 firewood stove, Turbo charcoal stove, Desha Shakthi saw dust pellet stove and Spectra saw dust pellet stove. Desha Shakthi stove shows the highest efficiency of 0.59 at high power operation while Spectra shows 0.43 and fallen in to the tier 4 of IWA matrix. Turbo charcoal stove categorized in to tire 2 as it is having thermal efficiency of 0.26. Anagi-2 and semi-enclosed stoves can be categorized in to tire 1 since they are having efficiencies of 0.17 and 0.15 respectively. Anagi- 2 stove shows the lowest time to boil while DeshShakthi stove takes highest time to boil water. Desha Shakthi stove shows lowest burning rate which is 5 g/min while Anagi -2 shows the highest burning rate of 28.65g/min. Specific fuel consumption of Desha Shakthi is the lowest as 0.05 kg of fuel per kg of water while semi-enclosed stoves shows the highest as 0.16. and high storage and Overall average specific energy consumption of Desha Shakthi stove is the lowest as 1.10 kJ/kg of water and highest of Anagi-2 as it is 5.27 kJ/kg of water. The highest fire power of 8712.71 W is shown by Anagi-2 while Desha Shakthi has the lowest fire power as 1279.58 W. To categories stove emissions and safety under IWA performance matrix, the emission tests also should be done during the WBT. When comparing the designs ofstoves there is a possibility of improving the performance of Spectra stove by introducing design modifications.
item: Conference-Full-text
Evaluation of rans turbulence models for prediction of lateral film cooling effectiveness at low blowing ratios
(IEEE, 2021-07) Sanjeeva, P; Thilakarathna, E; Mallikarachchi, C; Ranasinghe, C; Adhikariwatte, W; Rathnayake, M; Hemachandra, K
Accuracy of numerical predictions of film cooling performance is vital to investigate for designing and analyzing film cooling technology. Three RANS turbulence models of Standard k- ε (SKE), Standard k- ω (SKW) and Shear Stress Transport methods (SST k- ω ) were selected and used to simulate low blowing ratio cases ( M<1 ). The three blowing ratio of 0.2, 0.5 and 0.7 were produced using an inclined cylindrical hole of 30 degree made on a flat plate. ANSYS CFX solver was used to simulate the selected experimental cases with density ratio (DR) of 1.8. The numerical results of the three turbulence models under the blowing rate of 0.2 have not captured the lateral distribution of coolant correctly. SKW under the blowing rate of 0.5 have accurately predicted the effectiveness in mixing region. Centerline adiabatic effectiveness generated by SKW model was in a good agreement with experimental results for the blowing rate of 0.5. For the blowing rate of 0.2, the centerline effectiveness were best predicted by the SST model while SKW and SKE models can be used to predict the adiabatic effectiveness with considerable accuracy in lateral direction in the region of X/D<10 .
item: Conference-Full-text
Heat transfer enhancement in microchannels with liquid - liquid slug flow using al2o3 nanoparticles
(IEEE, 2022-07) Siriwardana, G; Bandara, T; Ranasinghe, C; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
Non–mixing two-phase flows in microchannels have become a popular technique for cooling applications due to their thermal performance and flow generation simplicity. Slugflow is one of the regimes in two-phase flow that has higher rates of heat and mass transfer in microchannels compared to other types because of the internal fluid recirculation within the slugs. The addition of nanoparticles to one of the phases in slug-flow could further increase the heat transfer rates. Therefore, in this research, nanofluid-based liquid-liquid slug-flow was studied. Studies were carried out numerically using ANSYS Fluent®. A series of studies were carried out to investigate the effect of nanoparticles on heat transfer. Aluminium oxide (Al 2 O 3 ) was selected as nanoparticles due to its physical and chemical stability along with its high thermal conductivity. Numerical results were validated with the experimental data available in the literature. Interface capturing of two-phase flow was done using VOF (Volume-of-Fluid) and Eulerian–Eulerian mixture models. The results showed a significant heat transfer enhancement when using nanoparticles in either phase. Two-phase slug-flow itself has shown up to four-times the increase in heat transfer in terms of Nusselt Number in the literature. This could be increased by more than eightfold by incorporating nanoparticles into the secondary phase.
item: Article-Full-text
How can we turn heat into useful energy using nanotechnology?
(2023-08) Henadeera, P; Samaraweera, N; Ranasinghe, C; Wijewardane, A
In 1821, the German physicist Thomas Seebeck made a groundbreaking discovery that revealed the direct conversion of heat energy into electricity. He did so by bringing two different metals together and holding one end heated and the other end cooled. This process is famously known as the Seebeck effect. William Thomson, a British physicist later known as Lord Kelvin, further developed the concept of thermoelectric circuits and introduced the idea of a temperature-dependent voltage in a circuit made of two dissimilar metals. Lord Kelvin’s contribution to the field of thermoelectricity paved the way for various applications in temperature sensors, power generators, refrigeration, and cooling systems.