Jundika Candra Kurnia - Academia.edu (original) (raw)

Papers by Jundika Candra Kurnia

Lecture notes in mechanical engineering, 2024

International Journal of Energy Research, Apr 27, 2020

The geothermal potential available from deep underground mines has yet to be utilized. However, s... more The geothermal potential available from deep underground mines has yet to be utilized. However, stope-coupled heat exchangers (SCHE) are aiming to take advantage of the unused low-grade geothermal energy. Backfilled stopes provide a unique opportunity to install nonlinear heat exchangers, as the geometry is not limited to the shape of a borehole. Helical pipes deliver superior fluid mixing and heat exchange compared to straight pipes, due to the effect of the secondary flow within the helical pipe. The helical closed-loop geothermal heat exchanger enables the backfilled stopes of the mine to be repurposed as thermal energy storage units. This article delves into the experimental results from a unique state-of-the-art laboratory scale helical closedloop heat exchanger with varying thermophysical parameters. Additionally, a novel conjugate numerical model is developed and its results are validated against the base case of the experimental studies. Additionally, the numerical model is validated in a spatial-temporal sense with thermocouple data from the experimental rig. The numerical model is also applied to a helical SCHE situated within a backfilled stope for the first time. The results of the numerical model suggest that the pumping rate through the SCHE has a significant effect on the heat exchange rate and the overall energy transfer between the SCHE and the backfill. Additionally, the temperature contours from the numerical model suggest that a decreased pitch/helical diameter will increase the storage capacity of the helical SCHE. Overall, an average of 2.5 MW can be stored over the first 4 days of geothermal charging with the investigated fullscale SCHE, boasting a pseudo-steady-state storage rate of 1.7 MW.

Energy Procedia, Feb 1, 2019

District heating networks are commonly addressed in the literature as one of the most effective s... more District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand-outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.

Chemical Engineering and Processing, Nov 1, 2022

Renewable Energy, Sep 1, 2021

Abstract Abandoned oil well can be a promising alternative to be retrofitted to extract geotherma... more Abstract Abandoned oil well can be a promising alternative to be retrofitted to extract geothermal energy than the conventional geothermal well. This study investigates the potential of converting abandoned oil well into geothermal energy power plant by combining computational fluid dynamics (CFD) simulation, process simulation, and techno-economic analysis. A detailed CFD model was formulated and validated with verified data from published literature. The model was then utilized to study key performance variables on heat extractions coupled with the Organic Rankine Cycle (ORC) to generate power and its subsequent techno-economic analysis. The results indicate that, due to relatively low temperature profile in typical Malaysian wells, the Levelized Cost of Electricity (LCOE) of the ORC system was found to be almost double than that of conventional geothermal technologies. To reduce the LCOE, at least four abandoned wells in a close proximity are required. Alternatively, other renewable energy sources (e.g., solar, biomass) could be used to upgrade the geothermal well. This techno-economic analysis shall serve as a preliminary assessment on the feasibility of utilizing abandoned oil wells in Malaysia for geothermal energy extraction.

International Journal of Thermal Sciences, Jun 1, 2021

Abstract Conjugate heat transfer of liquid-gas fin and tube heat exchangers is widely used in ind... more Abstract Conjugate heat transfer of liquid-gas fin and tube heat exchangers is widely used in industry. However, heat transfer characteristics of such system is difficult to predict as the limiting heat rate can be from either side. This paper aims to quantify the conjugate heat transfer performance of fin and tube heat exchangers via mathematical modeling. Three-dimensional conjugate fluid flow and heat transfer model is developed and validated against the state-of-the-art experimental data and existing analytical correlations. Turbulent k-e model has been employed for the fluid flow and heat transfer modeling. Statistical method, i.e. data reduction and multivariate nonlinear regression techniques, is implemented to analyse the results and to quantify the interaction between parameters. Wide range of parametric studies and simulations is further carried out to evaluate the significance of design, geometrical and operating parameters. According to the results of the study, larger fin length factor and fin pitch and the smaller tube diameter are in favor of fin and tube heat exchangers within the Reynolds number range of 3000–12,000. Finally, a novel conjugate heat transfer correlation for liquid-gas finned tube heat exchangers is proposed to assist engineers for practical designs and applications. The results suggest that our new correlation gives rise to a more accurate conjugate heat transfer prediction as compared to that of traditional non-conjugate counterpart.

Energy, Dec 1, 2019

While the ability to access a small fraction of data records from a large volume of scientific da... more While the ability to access a small fraction of data records from a large volume of scientific datasets is vital to accelerate scientific discovery, existing parallel file systems face serious challenges in managing scientific big data since data services have traditionally been decoupled from file systems. In this paper, we present IndexIt, an in-situ index and query middleware that aims to enhance record locating services for parallel file systems. When applications are writing data to parallel file systems, IndexIt allows users to index data while they are still in memory and bypass the performance bottleneck between memory and disks. By applying lightweight Bitmap-Range index and organizing the index as key-value pairs, IndexIt accelerates index building efficiently. Moreover, we propose a twolevel query processing framework to process query requests. We build a prototype and evaluate its performance with real scientific datasets. Compared with existing data management tools, the index building time can be reduced dramatically. The proposed two-level query processing achieves up to 3 orders of magnitude speed-up than scanning the entire dataset and shows up to 1.35x speed-up than an existing tool.

Lecture notes in mechanical engineering, Oct 4, 2022

The heat transfer and flow of nanofluids in microchannel heat sink is usually numerically investi... more The heat transfer and flow of nanofluids in microchannel heat sink is usually numerically investigated by the single-phase model. The thermal conductivity and viscosity of nanofluids are calculated in the whole computational region because the single-phase model, assumes the nanofluids is static and nanoparticles concentration is uniform. However for the actual forced flow process, the concentration distribution of the nanofluids is not uniform. So the thermal properties of the nanofluids vary within different computational regions. With the increase of the velocity of the nanofluids, the deviation between the prediction of single-phase model and experimental results increases. In this paper, a new simulation method is proposed to consider the inhomogeneous and dynamic thermophysical properties of the nanofluids by obtaining the nonuniformly distributed nanoparticle concentration in each numerical cell. At the same time, it takes into account the following factors: the interactions between the nanoparticles, the solid wall and the base fluid, the axial conduction, the slip boundary conditions and fluid-solid coupling. The results show that the proposed numerical simulation method further improve the simulation accuracy for the forced flow and heat transfer process of nanofluids in the microchannel in a wider range. The effects of the nanoparticles concentration, Reynolds number and axial heat transfer on the thermophysical properties of the nanofluilds, the flow and heat transfer characteristics of a rectangular microchannels with hydraulic dimensions of 341 μm were analyzed using the proposed simulation model. The main results are as follows: the nanoparticles are enriched at the near wall for the fully developed region; the nonuniformity of the nanofluilds thermal conductivity coefficient distribution at the channel cross section increases with the increase of the mass flow rate and the inlet centration; under the same Reynolds number, the higher the nanofluids concentration the better the heat transfer characteristics, but there is no linear relationship between the enhancement amplitude and concentration; the heat transfer coefficient of nanofluid with 1% and 2% alumina nanoparticles concentration is about 5.86% and 8.49% higher than that of deionized water, respectively; the axial conduction effect cannot be ignored for the microchannel, which significantly affects the inlet and outlet region of the microchannel especially when the Reynolds number is low. The nanofluilds temperature in the microchannel increases with the curve and does not match the conventional linear growth hypothesis.

International Journal of Automotive and Mechanical Engineering, Mar 30, 2020

Symbol Vp bubble volume, m 3 Ab area of influence K empirical constant Ai interfacial area densit... more Symbol Vp bubble volume, m 3 Ab area of influence K empirical constant Ai interfacial area density, 1/m Greek alphabets Aif interfacial area concentration, 1/m diffusivity, m 2 /s Cp specific heat, J/kg K ρ density, kg/m 3 din inner tube diameter, m

Lecture notes in mechanical engineering, Oct 4, 2022

MATEC web of conferences, 2018

As a lot of people spend their time indoor, indoor thermal comfort will affect the performance of... more As a lot of people spend their time indoor, indoor thermal comfort will affect the performance of the occupants in terms of health, comfort and productivity. This paper aims to investigate the thermal comfort of an office building constructed using low cost materials in tropical climate condition. That has been achieved by investigating the PMV using the CBE thermal comfort tool in the postgraduate office building in the solar research site in UTP. The experimental measurements have been conducted at two different cases; without ventilation and with air-conditioned in the office building. The thermal comfort of the office building is assessed by using the ASHRAE thermal sensation scale. Results have demonstrated that the office room without ventilation is hot and not suitable for occupants to work at such thermal environment. Thermal comfort of the room with airconditioning is warm and is slightly better than the room without ventilation as the PMV has been improved by around 60%. However, the acceptable thermal comfort level in the low-cost material office building is yet to be achieved.

Industrial & Engineering Chemistry Research, Dec 15, 2021

Applied Energy, Oct 1, 2019

• A comprehensive review of researches on PEMFC operates in dead-end anode. • Performance deterio... more • A comprehensive review of researches on PEMFC operates in dead-end anode. • Performance deterioration due to hydrogen starvation, water accumulation and nitrogen crossover. • Purging strategy to recover cell and stack performance are evaluated. • Alternatives method to recover stack performance are analyzed. • Future research directions to improve dead-end anode operation are discussed.

Energy Procedia, Aug 1, 2015

Energy conversion efficiency of a thermo photo voltaic (TPV) system strongly depends on the wall ... more Energy conversion efficiency of a thermo photo voltaic (TPV) system strongly depends on the wall temperature and its uniformity. Therefore, improving heat transfer characteristics of these systems is a focus of many recent studies. Significant efforts have been devoted to investigate flame stabilization and heat transfer enhancement for straight channels; planar and circular. However, the investigation of the impact of curvature on heat transfer and flow characteristics of a reacting flow is limited, implying that more studies are required. This study explores the effect of curvature on heat transfer, pressure drop and emission levels for a circular micro-combustor with sudden expansion (backward facing step). The study uses steady state Reynolds Average Numerical Simulation (RANS) turbulence model along with a finite rate chemistry model to numerically investigate the flame structure inside a microcombustor. The investigation observes significant enhancement in outer wall temperature and heat flux for curved ducts as compared to those for straight channels.

Applied Energy, Sep 1, 2019

• Novel ground coupled seasonal thermal energy storage for heating and cooling is evaluated. • La... more • Novel ground coupled seasonal thermal energy storage for heating and cooling is evaluated. • Laboratory scale proof-of-concept and model validation are demonstrated. • Utilization of sensible and latent heat of wet ground for thermal storage. • High resolution weather data from four Canadian cities are compared with idealized sinusoidal data. • Control scheme can improve energy extraction and storage for heating and cooling.

Applied Energy, Feb 1, 2021

Abstract Fuel cell is considered as a promising candidate to replace internal combustion engine i... more Abstract Fuel cell is considered as a promising candidate to replace internal combustion engine in the future vehicles amid growing interest to lessen environment degradation due to fossil fuel burning. To achieve successful adoption of fuel cell-based power train, a simple and reliable fuel cell system is required. Open cathode fuel cell is one of such systems which offers simple configuration where the ambient air is used directly to provide cooling and serve as an oxidant, thus eliminating the requirement for a complex air supply subsystem, minimizing parasitic load and reducing overall cost of the system. The major challenge with the open cathode configuration is the strong dependence of the stack performance on the ambient conditions. To address this issue, numerous studies evaluating the performance of open cathode fuel cell and various factors affecting it have been conducted and reported. Important findings from these studies are currently scattered, impeding the pace of research and development. To assist and expedite further research and development of open cathode fuel cell and accelerate its mass application, it is imperative to extract and discuss the important findings of previous studies and identify the gap that requires further attention. This paper presents a comprehensive review of the current development of open cathode fuel cell and identifies various aspects that can potentially influence its future advancements. In addition, the research and development needs for further growth of the field are highlighted and discussed.

ECS transactions, Apr 24, 2022

2014 AGU Fall Meeting, Dec 18, 2014

Applied Thermal Engineering, Jun 1, 2016

Abstract This study evaluates heat transfer performance and entropy generation of laminar flow in... more Abstract This study evaluates heat transfer performance and entropy generation of laminar flow in coiled tubes with various cross-sections geometries i.e. circular, ellipse and square, relatives to the straight tubes of similar cross-sections. A computational fluid dynamics model is developed and validated against empirical correlations. Good agreement is obtained within range of Reynolds and Dean numbers considered. Effect of geometry, wall temperature, Reynolds number and heating/cooling mode were examined. To evaluate the heat transfer performance of the coiled tube configurations, a parameter referred as Figure of Merit (FoM) is defined as the ratio heat transfer rate to the required pumping power. In addition, exergy analysis is carried out to examine the inefficiency of the coiled tube configurations. The results indicate that coiled tubes provide higher heat transfer rate. In addition, it was found to be more efficient as reflected by lower entropy generation as compared to straight tubes. Among the studied cross-section, square cross-section generates the highest entropy, followed by ellipse and circular counterpart. Entropy production from heat transfer contribution is two order-of-magnitude higher than that of entropy contribution from viscous dissipation. Cooling case produces slightly higher entropy than heating counterpart. Finally, this study can provide practical guideline to design more efficient coiled heat exchanger.

Lecture notes in mechanical engineering, 2024

International Journal of Energy Research, Apr 27, 2020

The geothermal potential available from deep underground mines has yet to be utilized. However, s... more The geothermal potential available from deep underground mines has yet to be utilized. However, stope-coupled heat exchangers (SCHE) are aiming to take advantage of the unused low-grade geothermal energy. Backfilled stopes provide a unique opportunity to install nonlinear heat exchangers, as the geometry is not limited to the shape of a borehole. Helical pipes deliver superior fluid mixing and heat exchange compared to straight pipes, due to the effect of the secondary flow within the helical pipe. The helical closed-loop geothermal heat exchanger enables the backfilled stopes of the mine to be repurposed as thermal energy storage units. This article delves into the experimental results from a unique state-of-the-art laboratory scale helical closedloop heat exchanger with varying thermophysical parameters. Additionally, a novel conjugate numerical model is developed and its results are validated against the base case of the experimental studies. Additionally, the numerical model is validated in a spatial-temporal sense with thermocouple data from the experimental rig. The numerical model is also applied to a helical SCHE situated within a backfilled stope for the first time. The results of the numerical model suggest that the pumping rate through the SCHE has a significant effect on the heat exchange rate and the overall energy transfer between the SCHE and the backfill. Additionally, the temperature contours from the numerical model suggest that a decreased pitch/helical diameter will increase the storage capacity of the helical SCHE. Overall, an average of 2.5 MW can be stored over the first 4 days of geothermal charging with the investigated fullscale SCHE, boasting a pseudo-steady-state storage rate of 1.7 MW.

Energy Procedia, Feb 1, 2019

District heating networks are commonly addressed in the literature as one of the most effective s... more District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand-outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.

Chemical Engineering and Processing, Nov 1, 2022

Renewable Energy, Sep 1, 2021

Abstract Abandoned oil well can be a promising alternative to be retrofitted to extract geotherma... more Abstract Abandoned oil well can be a promising alternative to be retrofitted to extract geothermal energy than the conventional geothermal well. This study investigates the potential of converting abandoned oil well into geothermal energy power plant by combining computational fluid dynamics (CFD) simulation, process simulation, and techno-economic analysis. A detailed CFD model was formulated and validated with verified data from published literature. The model was then utilized to study key performance variables on heat extractions coupled with the Organic Rankine Cycle (ORC) to generate power and its subsequent techno-economic analysis. The results indicate that, due to relatively low temperature profile in typical Malaysian wells, the Levelized Cost of Electricity (LCOE) of the ORC system was found to be almost double than that of conventional geothermal technologies. To reduce the LCOE, at least four abandoned wells in a close proximity are required. Alternatively, other renewable energy sources (e.g., solar, biomass) could be used to upgrade the geothermal well. This techno-economic analysis shall serve as a preliminary assessment on the feasibility of utilizing abandoned oil wells in Malaysia for geothermal energy extraction.

International Journal of Thermal Sciences, Jun 1, 2021

Abstract Conjugate heat transfer of liquid-gas fin and tube heat exchangers is widely used in ind... more Abstract Conjugate heat transfer of liquid-gas fin and tube heat exchangers is widely used in industry. However, heat transfer characteristics of such system is difficult to predict as the limiting heat rate can be from either side. This paper aims to quantify the conjugate heat transfer performance of fin and tube heat exchangers via mathematical modeling. Three-dimensional conjugate fluid flow and heat transfer model is developed and validated against the state-of-the-art experimental data and existing analytical correlations. Turbulent k-e model has been employed for the fluid flow and heat transfer modeling. Statistical method, i.e. data reduction and multivariate nonlinear regression techniques, is implemented to analyse the results and to quantify the interaction between parameters. Wide range of parametric studies and simulations is further carried out to evaluate the significance of design, geometrical and operating parameters. According to the results of the study, larger fin length factor and fin pitch and the smaller tube diameter are in favor of fin and tube heat exchangers within the Reynolds number range of 3000–12,000. Finally, a novel conjugate heat transfer correlation for liquid-gas finned tube heat exchangers is proposed to assist engineers for practical designs and applications. The results suggest that our new correlation gives rise to a more accurate conjugate heat transfer prediction as compared to that of traditional non-conjugate counterpart.

Energy, Dec 1, 2019

While the ability to access a small fraction of data records from a large volume of scientific da... more While the ability to access a small fraction of data records from a large volume of scientific datasets is vital to accelerate scientific discovery, existing parallel file systems face serious challenges in managing scientific big data since data services have traditionally been decoupled from file systems. In this paper, we present IndexIt, an in-situ index and query middleware that aims to enhance record locating services for parallel file systems. When applications are writing data to parallel file systems, IndexIt allows users to index data while they are still in memory and bypass the performance bottleneck between memory and disks. By applying lightweight Bitmap-Range index and organizing the index as key-value pairs, IndexIt accelerates index building efficiently. Moreover, we propose a twolevel query processing framework to process query requests. We build a prototype and evaluate its performance with real scientific datasets. Compared with existing data management tools, the index building time can be reduced dramatically. The proposed two-level query processing achieves up to 3 orders of magnitude speed-up than scanning the entire dataset and shows up to 1.35x speed-up than an existing tool.

Lecture notes in mechanical engineering, Oct 4, 2022

The heat transfer and flow of nanofluids in microchannel heat sink is usually numerically investi... more The heat transfer and flow of nanofluids in microchannel heat sink is usually numerically investigated by the single-phase model. The thermal conductivity and viscosity of nanofluids are calculated in the whole computational region because the single-phase model, assumes the nanofluids is static and nanoparticles concentration is uniform. However for the actual forced flow process, the concentration distribution of the nanofluids is not uniform. So the thermal properties of the nanofluids vary within different computational regions. With the increase of the velocity of the nanofluids, the deviation between the prediction of single-phase model and experimental results increases. In this paper, a new simulation method is proposed to consider the inhomogeneous and dynamic thermophysical properties of the nanofluids by obtaining the nonuniformly distributed nanoparticle concentration in each numerical cell. At the same time, it takes into account the following factors: the interactions between the nanoparticles, the solid wall and the base fluid, the axial conduction, the slip boundary conditions and fluid-solid coupling. The results show that the proposed numerical simulation method further improve the simulation accuracy for the forced flow and heat transfer process of nanofluids in the microchannel in a wider range. The effects of the nanoparticles concentration, Reynolds number and axial heat transfer on the thermophysical properties of the nanofluilds, the flow and heat transfer characteristics of a rectangular microchannels with hydraulic dimensions of 341 μm were analyzed using the proposed simulation model. The main results are as follows: the nanoparticles are enriched at the near wall for the fully developed region; the nonuniformity of the nanofluilds thermal conductivity coefficient distribution at the channel cross section increases with the increase of the mass flow rate and the inlet centration; under the same Reynolds number, the higher the nanofluids concentration the better the heat transfer characteristics, but there is no linear relationship between the enhancement amplitude and concentration; the heat transfer coefficient of nanofluid with 1% and 2% alumina nanoparticles concentration is about 5.86% and 8.49% higher than that of deionized water, respectively; the axial conduction effect cannot be ignored for the microchannel, which significantly affects the inlet and outlet region of the microchannel especially when the Reynolds number is low. The nanofluilds temperature in the microchannel increases with the curve and does not match the conventional linear growth hypothesis.

International Journal of Automotive and Mechanical Engineering, Mar 30, 2020

Symbol Vp bubble volume, m 3 Ab area of influence K empirical constant Ai interfacial area densit... more Symbol Vp bubble volume, m 3 Ab area of influence K empirical constant Ai interfacial area density, 1/m Greek alphabets Aif interfacial area concentration, 1/m diffusivity, m 2 /s Cp specific heat, J/kg K ρ density, kg/m 3 din inner tube diameter, m

Lecture notes in mechanical engineering, Oct 4, 2022

MATEC web of conferences, 2018

As a lot of people spend their time indoor, indoor thermal comfort will affect the performance of... more As a lot of people spend their time indoor, indoor thermal comfort will affect the performance of the occupants in terms of health, comfort and productivity. This paper aims to investigate the thermal comfort of an office building constructed using low cost materials in tropical climate condition. That has been achieved by investigating the PMV using the CBE thermal comfort tool in the postgraduate office building in the solar research site in UTP. The experimental measurements have been conducted at two different cases; without ventilation and with air-conditioned in the office building. The thermal comfort of the office building is assessed by using the ASHRAE thermal sensation scale. Results have demonstrated that the office room without ventilation is hot and not suitable for occupants to work at such thermal environment. Thermal comfort of the room with airconditioning is warm and is slightly better than the room without ventilation as the PMV has been improved by around 60%. However, the acceptable thermal comfort level in the low-cost material office building is yet to be achieved.

Industrial & Engineering Chemistry Research, Dec 15, 2021

Applied Energy, Oct 1, 2019

• A comprehensive review of researches on PEMFC operates in dead-end anode. • Performance deterio... more • A comprehensive review of researches on PEMFC operates in dead-end anode. • Performance deterioration due to hydrogen starvation, water accumulation and nitrogen crossover. • Purging strategy to recover cell and stack performance are evaluated. • Alternatives method to recover stack performance are analyzed. • Future research directions to improve dead-end anode operation are discussed.

Energy Procedia, Aug 1, 2015

Energy conversion efficiency of a thermo photo voltaic (TPV) system strongly depends on the wall ... more Energy conversion efficiency of a thermo photo voltaic (TPV) system strongly depends on the wall temperature and its uniformity. Therefore, improving heat transfer characteristics of these systems is a focus of many recent studies. Significant efforts have been devoted to investigate flame stabilization and heat transfer enhancement for straight channels; planar and circular. However, the investigation of the impact of curvature on heat transfer and flow characteristics of a reacting flow is limited, implying that more studies are required. This study explores the effect of curvature on heat transfer, pressure drop and emission levels for a circular micro-combustor with sudden expansion (backward facing step). The study uses steady state Reynolds Average Numerical Simulation (RANS) turbulence model along with a finite rate chemistry model to numerically investigate the flame structure inside a microcombustor. The investigation observes significant enhancement in outer wall temperature and heat flux for curved ducts as compared to those for straight channels.

Applied Energy, Sep 1, 2019

• Novel ground coupled seasonal thermal energy storage for heating and cooling is evaluated. • La... more • Novel ground coupled seasonal thermal energy storage for heating and cooling is evaluated. • Laboratory scale proof-of-concept and model validation are demonstrated. • Utilization of sensible and latent heat of wet ground for thermal storage. • High resolution weather data from four Canadian cities are compared with idealized sinusoidal data. • Control scheme can improve energy extraction and storage for heating and cooling.

Applied Energy, Feb 1, 2021

Abstract Fuel cell is considered as a promising candidate to replace internal combustion engine i... more Abstract Fuel cell is considered as a promising candidate to replace internal combustion engine in the future vehicles amid growing interest to lessen environment degradation due to fossil fuel burning. To achieve successful adoption of fuel cell-based power train, a simple and reliable fuel cell system is required. Open cathode fuel cell is one of such systems which offers simple configuration where the ambient air is used directly to provide cooling and serve as an oxidant, thus eliminating the requirement for a complex air supply subsystem, minimizing parasitic load and reducing overall cost of the system. The major challenge with the open cathode configuration is the strong dependence of the stack performance on the ambient conditions. To address this issue, numerous studies evaluating the performance of open cathode fuel cell and various factors affecting it have been conducted and reported. Important findings from these studies are currently scattered, impeding the pace of research and development. To assist and expedite further research and development of open cathode fuel cell and accelerate its mass application, it is imperative to extract and discuss the important findings of previous studies and identify the gap that requires further attention. This paper presents a comprehensive review of the current development of open cathode fuel cell and identifies various aspects that can potentially influence its future advancements. In addition, the research and development needs for further growth of the field are highlighted and discussed.

ECS transactions, Apr 24, 2022

2014 AGU Fall Meeting, Dec 18, 2014

Applied Thermal Engineering, Jun 1, 2016

Abstract This study evaluates heat transfer performance and entropy generation of laminar flow in... more Abstract This study evaluates heat transfer performance and entropy generation of laminar flow in coiled tubes with various cross-sections geometries i.e. circular, ellipse and square, relatives to the straight tubes of similar cross-sections. A computational fluid dynamics model is developed and validated against empirical correlations. Good agreement is obtained within range of Reynolds and Dean numbers considered. Effect of geometry, wall temperature, Reynolds number and heating/cooling mode were examined. To evaluate the heat transfer performance of the coiled tube configurations, a parameter referred as Figure of Merit (FoM) is defined as the ratio heat transfer rate to the required pumping power. In addition, exergy analysis is carried out to examine the inefficiency of the coiled tube configurations. The results indicate that coiled tubes provide higher heat transfer rate. In addition, it was found to be more efficient as reflected by lower entropy generation as compared to straight tubes. Among the studied cross-section, square cross-section generates the highest entropy, followed by ellipse and circular counterpart. Entropy production from heat transfer contribution is two order-of-magnitude higher than that of entropy contribution from viscous dissipation. Cooling case produces slightly higher entropy than heating counterpart. Finally, this study can provide practical guideline to design more efficient coiled heat exchanger.