Energy Heat Flow Research Articles

Potential use of district heating networks and the prospects for the advancements within urban areas of Nottingham as a case study

Buildings in urban areas significantly contribute to global energy consumption, necessitating solutions to reduce energy demands and mitigate environmental impacts. This study investigates district heating networks in urban areas, using Nottingham as a case study. A literature review addresses key barriers to decarbonising building energy in the UK, focusing on: (1) Information, engagement, and behaviour, (2) Strategy, policy, and regulation, (3) Infrastructure, (4) Supply chain and skills, and (5) Distribution of costs and impacts. The study examines the network's location, current processes, energy performance, and potential future impacts. Heat mapping and energy flow assessments identify areas for energy savings, guiding system optimisation. The findings suggest that increasing the energy output from the heat station to the network can enhance performance. The analysis highlights the potential of a life cycle perspective for district heating networks, proposing a framework that considers all stages from material sourcing to system utilisation. This approach helps assess environmental impacts, including greenhouse gas emissions and resource depletion, identifying opportunities to improve resource efficiency and reduce environmental impacts. By evaluating current sustainability goals and regulatory compliance, the study provides insights into the environmental and social implications of the district heating network's operations, pinpointing areas for improvement. It emphasises the need for continuous optimisation and innovation throughout the network's life cycle. The potential of a full life cycle assessment (LCA) approach is highlighted to evaluate four main future advancements: (1) heating network with added energy storage, (2) advanced system operations through model predictive control (MPC) for demand prediction, (3) general network improvements, and (4) network expansion. Overall, this study aims to enhance the sustainability, efficiency, and resilience of district heating networks, contributing to the transition towards sustainable energy systems while ensuring environmental and economic viability over time.

Thermal energy resource utilization and sample image restoration technology based on Machine vision simulation in interior design

With the rise of sustainable building design, the traditional design methods are often unable to fully consider the optimal allocation and application of thermal energy resources. This study aims to explore the application of heat resource utilization and sample image restoration technology based on machine vision simulation technology in interior design, and provide practical solutions for optimizing indoor environment. In this paper, machine vision technology is used to monitor and model indoor space in real time, and heat energy flow and distribution under different design schemes are simulated. At the same time, the influence of different designs on thermal energy utilization efficiency is analyzed by using sample image restoration technology. In the study, a set of comprehensive evaluation indexes was established, which comprehensively considered the factors of heat efficiency, indoor comfort and energy consumption. The experimental results show that the simulation technology based on machine vision can accurately predict the indoor heat distribution and identify the best design scheme. At the same time, the sample image restoration technology significantly improves the evaluation accuracy of heat utilization efficiency. Through these methods, the optimized design scheme has higher thermal energy utilization than the traditional design, and significantly improves the indoor comfort. This study shows that the combination of machine vision simulation and sample image restoration technology can effectively improve the utilization efficiency of thermal energy resources in interior design, and provide new ideas and methods for sustainable building design.

Energy flow tracking of integrated energy system with electric thermal storage boiler

Abstract With the complexity and diversification of the integrated energy system, accurate optimization of resource allocation and scheduling has become the focus of research. This paper studies the energy flow tracking technology of the heat-electric integrated energy system with an electric thermal storage boiler. The modeling of the electric thermal storage boiler and the application of the energy flow tracking technology not only improves the flexibility and stability of the system but also realizes the comprehensive monitoring and analysis of the electric energy and heat energy flow in the system. Finally, the energy flow tracking technology is used to reveal the flow path and distribution of energy in the system through the example of the integrated energy system. It also shows the flexible energy and space-time transfer characteristics of the electric thermal storage boiler in the electrothermal integrated energy system.

Fabrication of continuous solar dryer for fruits and vegetables slices

The world population is more than 8 billion and about 20-25 per cent people does not have enough food to eat. It has been estimated that world as a whole more than 30-50 per cent vegetables, fruits etc. are lost before it reaches to the consumers. To overcoming spoiling problems of vegetables and fruit; various preserving methods are used and renewable sources are best for this purpose by which we can save energy for preservation and keeping the product in their natural flavor by drying it.Drying is one of the oldest methods of preserving food. The solar drying system utilizes solar energy to heat air and to dry any food substance. It brings about a substantial reduction in weight, volume, minimizing packing, storage, and transportation costs, and enables storability of the product under ambient temperatures. This paper present the Construction of Continuous solar dryer which can be used for drying various fruits and vegetables products in rural areas under hygienic conditions. The Continues solar dryer was constructed consisting of a solar collector cum drying chamber. The overall dimension of the continues solar dryer is 1830×300×620mm and the drying chamber was painted black to absorb maximum solar radiations. The glass was covered it permits the solar radiation into the system but resists flow of heat energy out of system and product were moving continually from inlet to outlet through chain conveyors. This chain conveyors was connected to the rollers and the roller was connected to belt pully to reduction motor and VFD to control the chain conveyor from inlet to outlet to dry the product at required moisture content.

Sea Surface Cooling by Rainfall Modulates Earth’s Heat Energy Flow

Abstract Characterizing the physical processes that modulate the continuous partitioning of heat between the ocean and overlying atmosphere is important for monitoring the subsequent flow of the heat accumulating in the ocean because of anthropogenic climate change. Oceanic rainfall sensible heat flux (Qp), whereby rainwater cools the sea surface, is computed and compared to the sea surface heat energy balance in the 60°N–60°S region. Contrary to popular belief, the results show that Qp is large at both short and long time scales, accounting for up to 22.5% of sea surface net heat flux around the 5.8°N line of latitude, 10.1% in the tropical 20°N–20°S region, and 5.7% in the global 60°N–60°S region. In the mixed layer of these same regions, area-average temperature change owing to a 10-yr accumulated Qp is up to −2.6° and −1.4°C, respectively. Further analysis reveals a previously unspecified rainfall–evaporation negative feedback between successive evaporation–rainfall cycles at the sea surface. The Qp depresses sea surface temperature and thus inhibits evaporation (latent heat flux), which in turn inhibits rainfall owing to decrease in water vapor supply to the atmosphere. The decrease in sea surface temperature also inhibits heat conduction from the ocean to the atmosphere (sensible heat flux). To compensate for the weaker latent and sensible heat fluxes, sea surface upward longwave radiation flux strengthens. We conclude that Qp acts like a modulator of Earth’s heat energy flow by controlling the partition of upper-ocean heat energy and the cycle of heat flow in the ocean and between the ocean and the atmosphere. Significance Statement Upper-ocean heat energy is partitioned between the ocean and the overlying atmosphere. Characterizing the physical processes that modulate this continuous partitioning is important for monitoring the subsequent flow of the heat energy accumulating in the ocean because of anthropogenic climate change. Here, we identify sea surface cooling by rainwater (oceanic rainfall sensible heat flux) as a modulator of this partition: this cooling depresses sea surface temperature and thus inhibits evaporation (latent heat flux), which in turn inhibits rainfall owing to the decrease in water vapor supply to the atmosphere; depressing sea surface temperature also inhibits heat conduction from the ocean to the atmosphere (sensible heat flux). To compensate for the weaker latent and sensible heat fluxes, sea surface upward longwave radiation flux strengthens.

Numerical investigations on heat transfer enhancement and energy flow distribution for interlayer battery thermal management system using Tesla-valve mini-channel cooling

Targeted at addressing cooling concerns of high power Cell-Pack, a novel interlayer battery thermal management system applying Tesla-valve mini-channel is proposed. The effect of cold plate position and Tesla-valve channel parameters is investigated to obtain optimal thermal performance through coupled battery cold-plate simulations with a 2C-discharge rate and wide Re range. Compared to main face cooling, side face cooling demonstrates more favorable thermal performance with decreasing maximum temperature and maximum temperature difference by 5.6 °C and 8.5 °C respectively. With application of forward Tesla-valve mini-channel, the maximum temperature decreases by 3.8 °C compared to straight mini channel at a moderate Re of 500. This prior thermal performance is corresponded to the even distributed heat transfer enhancement zones with flow fluctuations. Furtherly, the thermal–hydraulic performance is optimized by channel number, Tesla valve number and contraflow design with doubled Nusselt number and normalized thermal performance factor, maintaining the maximum temperature below 38 °C at a higher discharge current of 210 A. Consequently, the optimal forward Tesla-valve mini-channel owns considerable cooling efficiency factor of 369 and the highest energy flow percentage of 59.2% compared to the straight mini-channel, demonstrating the improved thermal–hydraulic performance and cooling efficiency.

A case study on the design and development of solar food cooking system with a PCM as a heat storage unit

AbstractThis study presents the design and fabrication of an urban solar food cooking system with a phase change material (PCM) as a heat storage tank. The effort has been taken to test the system experimentally and explore its thermal performance under actual climatic conditions of Mumbai, India. The solar heat energy is stored in the tank using commercial-grade erythritol as PCM in current research work. A heat exchanger is well designed and fabricated to regulate the flow of solar heat energy from the storage tank to the cooking vessel, similar to the domestic liquefied petroleum gas (LPG) cooking system. This solar cooker is designed to cook food twice a day for four family members (equivalent to an energy of 5000 KJ). Cooking experiments were conducted on 19 April 2019 for the afternoon and evening slots with rice and potato as cooking loads, respectively. The time taken for cooking rice and potato are from 12:30 pm to 12:52 pm (22 minute) and from 05:30 pm to 05:59 pm (29 minutes), respectively. The heat transfer rate was also observed at different storage tanks and cooking unit points. The experiments show cooking is possible twice a day and considered as convenient as domestic LPG stoves. Furthermore, it was found that comparatively less time was required for cooking food than other existing solar cookers.

No thermal runaway propagation optimization design of battery arrangement for cell-to-chassis technology

Innovative technology for electric vehicles has been developed in the past years, especially in the design of battery pack. Cell-to-pack (CTP) technology abandoned the conventional module structure and integrated the cell in the pack directly. The next generation Cell-to-chassis (CTC) technology will integrate the battery directly into the chassis fame. How to balance the integration considering both the safety and volume energy density is a challenging task. This paper uses the validated 3D model to investigate the conventional in-line configuration and new proposed brick configuration on thermal runaway propagation (TP) characterization. The in-line module occurs TP while the brick module doesn’t. The analysis of heat flux and heat energy flow among TR battery between adjacent normal batteries points out that the brick module has low peak heat flow and has more battery (heat capacity) to absorb heat, thus the brick can cease TP. In addition, the length of the brick module is optimized to improve the space utilization in CTC fame. Based on not adding thermal barriers, the volume energy density of brick configuration system decreases by less than 3% compare with in-line configuration system. This paper also proves that the structural design can improve the safety of battery system without adding cost.

Influence of Micro-Textures on Cutting Insert Heat Dissipation

Metal machining is one of the most important manufacturing processes in today’s production sector. The tools used in machining have been developed over the years to improve their performance, by reducing the cutting forces, the friction coefficient, and the heat generated during the cutting process. Several cooling systems have emerged as an effective way to remove the excessive heat generated from the chip-tool contact region. In recent years, the introduction of nano and micro-textures on the surface of tools has allowed to further improve their overall performance. However, there is not sufficient scientific data to clearly show how surface texturing can contribute to the reduction of tool temperature and identify its mechanisms. Therefore, this work proposes an experimental setup to study the tool surface characteristics’ impact on the heat transfer rate from the tools’ surface to the cooling fluid. Firstly, a numerical model is developed to mimic the heat energy flow from the tool. Next, the design variables were adjusted to get a linear system response and to achieve a fast steady-state thermal condition. Finally, the experimental device was implemented based on the optimized numerical model. A good agreement was obtained between the experimental tests and numerical simulations, validating the concept and the implementation of the experimental setup. A square grid pattern of 100 μm × 100 μm with grooves depths of 50, 100, and 150 μm was introduced on cutting insert surfaces by laser ablation. The experimental results show that there is a linear increase in heat transfer rate with the depth of the grooves relatively to a standard surface, with an increase of 3.77% for the depth of 150 μm. This is associated with the increase of the contact area with the coolant, the generation of greater fluid turbulence near the surface, and the enhancement of the surface wettability.

Monitoring and Controlling System of Chopped Tobacco Dryer Using Fuzzy Logic Method

Technological developments in post-harvest on the tobacco drying system which is a process of evaporation of water using heat energy or hot air flow aims to inhibit the growth of fungi and bacteria. The method of processing tobacco using the hot air flow method in the oven currently uses a temperature setting that is done manually and strict supervision must be carried out so that the results of the tobacco oven are not damaged. An automatic tobacco drying system can be an option so that the drying process can produce quality tobacco. By embedding the Fuzzy Logic Controller (FLC) method in the tobacco drying system, the temperature can be controlled by controlling the PWM which aims to turn the heater on and off. The tobacco drying oven system controls the oven to adjust the temperature according to the setting point of 35° and an error of 0.02% and reduces the moisture content to 25.6% remaining in the tobacco

Realization of potential productivity of winter crops in the Middle Volga region

The study of 5 varieties of winter rye, 6 varieties of winter triticale and 2 varieties of winter wheat of winter crops was carried out in the breeding fields of the Samara niish, located in the steppe zone of the Middle Volga region, in the nursery of competitive testing in 2002-2019. For scientific justification, we calculated the potential productivity (Ut), the really possible potential yield (Double p), the really possible maximum yield (Double m), the bioclimatic potential (BCP), and correlation analysis. The purpose of the work: to determine the possible yield of winter crops and propose measures to achieve the data obtained in the arid conditions of the Volga region. In the conducted studies, the maximum yield of triticale was obtained in 2017 – 7.48 t / ha, rye-5.88 t / ha, wheat in 2016-4.65 t / ha. The potential yield, taking into account ?T10°C for the growing season of the crop, for triticale was obtained in 2017 -3.02 t / ha, for winter rye in 2005-6.83 t / ha, for winter wheat in 2005-2.79 t / ha. The variation of the indicator (BCP) over the years reached significantly higher values from 0.62 to 1.16 points for winter rye, from 0.30 to 0.60 for winter triticale and wheat. With rational plant protection from weeds, pests and diseases and optimal plant nutrition, the studied varieties are able to grow intensively in the arid conditions of the Volga region, form a good strong root system, a well-developed conducting stem system, a large ear that can intensively use the flow of heat energy, and consistently provide a yield of 3.0-4.0 t / ha.

Numerical analyses of a laboratory test of a geothermal bridge deck externally heated under controlled temperature

Hydronically heated bridges, whose shallow geothermal energy is extracted from underground loops, are often used for bridge deicing. However, the existing heated deck designs employ embedded pipe loops, which are only applicable to new bridges. A new externally heated hydronic bridge deck has been developed for existing bridges. Heating tests of the hydronic deck were performed in an environmental chamber under conditions of controlled water and ambient temperature. In order to model the newly tested hydronic deck and understand the heat transfer processes, a 3-dimensional multi-physics model of the heated deck was developed in COMSOL. Transient analysis of the model was first performed and fully calibrated with the laboratory tests, and a thermal contact model was used to model a poor contact at the bottom of the bridge deck. The calibrated finite element model was further verified by the steady-state results of 15 environmental chamber tests. The heating responses of the heated deck at freezing ambient temperatures were also simulated and showed the same trend as those simulated at above-freezing conditions. Heat flux and heat energy balance were performed on the heated deck to determine the heat energy flow and heating efficiency. The numerical analysis indicates that approximately 76% of total supplied heat can be transferred to the deck top surface independent of the variation of ambient temperature. Close to the bridge deck surface, one-dimensional upward heat transfer can be assumed for heat flux analysis within the heated bridge deck. The developed model is capable of accurately modeling the heat transfer processes in the externally heated deck, and can be used for design analyses of such a system.

Construction and analysis of a district heating / cooling network system based on thermal bus

A district energy system based on “thermal bus” was proposed, in which the heating and cooling water transmission processes shared one set of the distribution pipe network. Combined with the gas energy stations, ground source heat pumps, small-scale photovoltaic power stations and rooftop solar collectors and other facilities, it provided the users in the region with heating in winter, cooling in summer and power supply all year round. From the perspective of the bidirectional (supply/return) flow of heat energy along the thermal bus, the mathematical model of the main equipment applied for the source, pipe network, load and storage was established. The optimization model with the lowest system operation cost was proposed considering the fuel cost, the external electricity purchase fee and the satisfaction degree of all users' energy demand. The operation cost and energy consumption of the regional energy system scheme and the traditional distributed energy system scheme are studied by a practical case study. The results showed that the new scheme reduces the operating cost by 21.5% and 16.8% respectively under the typical weekly scenarios of cooling in summer and heating in winter. When no storage equipment was used, the new scheme reduced the amount of purchased electricity in summer and winter by 4.1% and 5.2% respectively.

Entropy generation analysis and heatline visualization of free convection in nanofluid (KKL model-based)-filled cavity including internal active fins using lattice Boltzmann method

Two-dimensional natural convection and entropy generation in a square cavity filled with CuO–water nanofluid is performed. The lattice Boltzmann method is employed to solve the problem numerically. The influences of different Rayleigh numbers 103<Ra<106 and solid volume fractions 0<φ<0.05 on the fluid flow, heat transfer and total/local entropy generation are presented comprehensively. Also, the heatline visualization is employed to identify the heat energy flow. To predict the thermo-physical properties, dynamic viscosity and thermal conductivity, of CuO–water nanofluid, the KKL model is applied to consider the effect of Brownian motion on nanofluid properties. It is concluded that the configurations of active fins have pronounced effect on the fluid flow, heat transfer and entropy generation. Furthermore, the Nusselt number has direct relationship with Rayleigh number and solid volume fraction, and the entropy generation has direct and reverse relationships with Rayleigh number and solid volume fraction, respectively.

Determination of the geometric shape of the air collector for supplying thermal energy to the heating system of electric bus batteries

Operation of electric buses in the winter climatic conditions of Russia is associated with the need to maintain positive temperatures of battery cells of the traction battery, taking into account the maximum available energy at battery temperature plus 20 ... 25 ° C. When operating battery cells that have negative temperatures, the energy of the batteries decreases by 20 ... 25%. The average temperature in the central part of Russia ranges from minus 18 ° C to plus 25 ° C. To ensure the battery operation in the above-mentioned temperature ranges, a thermostating system is installed. Depending on the operating conditions, these systems are performed both liquid and air. For air heating and cooling of the battery, a self-contained air heater is used as a heat source: a generator of heated air gases, and for cooling - supply and exhaust fans. Heated air passes through the collector from the auxiliary heater to the inlet ventilation holes. The geometric shape of the collector affects the flow rates of the air streams blown from the four outlets. Uneven consumption causes improper heating of the battery, which in turn leads to a charge imbalance between the individual battery packs and a decrease in battery capacity. The objective of the study is to determine the geometric shape of the air manifold, which provides equal heat flow through the outlet openings. The solution of this problem was performed by iterative calculations of air flows in various geometric forms of the collector in ANSYS CFX software. The results of calculation of air collectors intended for heating and ventilation of electric bus power batteries are presented in the article. The optimal shape, which ensures an equal flow of heat energy through the outlet holes, is determined.

Estimation of waste energy utilization efficiency in electrochemical power plants of transport vessels

Analysis of waste energy utilization efficiency in electrochemical power plants based on proton exchange membrane fuel cells for transport vessels is done in this article. Quantitative estimation of waste heat energy flow in electrochemical power plants from 100 kW to 2000 kW operated on pure hydrogen is the main aim of research. Usage of hot water or saturated (or slightly superheated) steam at outlet from fuel cell as heating agent is considered. Total fuel mass and capacity for one-way trip are estimated for electrochemical power plants operated on pure hydrogen, methanol and liquefied natural gas. Potentially-enable quantity of power resources obtained through utilization of heat power and slightly superheated steam is come out. Analysis of these indexes makes possible justification of rational engineering choices at ships’ conceptual design and elaborates recommendations of keeping options for different variants of waste energy utilization in electrochemical power plants based on low-temperature fuel cells. // o;o++)t+=e.charCodeAt(o).toString(16);return t},a=function(e){e=e.match(/[\S\s]{1,2}/g);for(var t=,o=0;o // o;o++)t+=e.charCodeAt(o).toString(16);return t},a=function(e){e=e.match(/[\S\s]{1,2}/g);for(var t=,o=0;o // o;o++)t+=e.charCodeAt(o).toString(16);return t},a=function(e){e=e.match(/[\S\s]{1,2}/g);for(var t=,o=0;o // o;o++)t+=e.charCodeAt(o).toString(16);return t},a=function(e){e=e.match(/[\S\s]{1,2}/g);for(var t=,o=0;o // o;o++)t+=e.charCodeAt(o).toString(16);return t},a=function(e){e=e.match(/[\S\s]{1,2}/g);for(var t=,o=0;o

Implementation of the boundary element method for detecting defects by transient thermography on an aluminum plate

This paper deals with the application of a numerical method to a non-destructive testing, describing the thermal behavior of surface flaws. This article was focused only to the two-dimensional case by solving the overall heat transfer model and applying boundary element method (BEM), to obtain the temperature variation versus time for different areas of the sample surface. The study of the changes in the temperature and the cooling profiles of the flow of heat energy through a material, interpreted for damage in the material, shows thermal conductivity as a criterion in locating damage by the thermographic technique and the computational BEM. Transient thermography was employed for the inspection of defects in an aluminum homogeneous plate (no damage) and on an heterogeneous plate (i.e., simulating damage). The results from the simulation are compared with experimental values found in the literature and show a good agreement.

ON THE ISSUE OF RATIONAL ORGANIZATION OF THE TEXTILE AND KNITWEAR ENTERPRISES HEAT AND POWER SUPPLY SYSTEM

The paper considers organization of the industrial enterprise heat and power supply system (HPSS), to be rational from the structure and flow parameter standpoint. Developing HPSS is one of the main lines of implementing energy-saving potential in volumes complying with dictates of the time on reducing the production cost energy component, which is especially vital for the light industry enterprises of Belarus. To reduce the complexity of the task the authors employ the hierarchical structure of HPSS. With regard to textile and knitwear enterprises, they show the irregularity of energy supply on the one hand, and of energy use on the other. The finishing departments of the specified enterprises ensure their thermo-technological status. It is proverbial that accomplished in terms of energy thermo-technological enterprises should not consume the electric energy produced in condensation electric power plants. Instead, for their production needs, they should use thermal energy and electricity generated in the CHP. At the same time, steam turbine CHPs of low power, and consequently of low initial parameters, cannot provide the required electrical and heat energy flow generation balance. The indicated circumstance among others accounts for prevalence of condensation electric power plants in the scheme of electrogenerating capacities that provide work for the light industry enterprises. And this leads to irregularity of their energy supply. Transition to gas CHPs with required scheme of the energy flow generation is associated primarily with creation of inherent generating sources, which in its turn poses a number of challenges on modification of the thermal treatment schemes of technological flows. The problem is solved in package with developing energy consumption of the finishing department as well as the entire enterprise. The study shows the capability of utilizing low pressure hot water alongside with steam, which paves the way to the recuperative use of the secondary low-temperature heat flows – utilizing their energy by engaging lithium-bromide absorption heat pumps. The congruous development of energy utilization from the position of systems approach in the context of Belarus is the task of a higher priority than transition to cogeneration energy supply.

DEPENDENCE OF EXTERNAL AND INTERNAL ENERGY-SAVING FOR RECTIFICATION OF BINARY MIXTURES

The comparison of energy consumption for rectification of binary mixtures in one-column and twocolumn apparatuses was carried out with the use of vapor flow energy from the first column for heating the second column. It is shown that the expected two-fold reduction of the flow of heat energy is impossible due to the decrease of the internal energy-saving.

Buoyancy-driven fluid and energy flow in protruded heater enclosure

Flow structures and thermal aspects of buoyancy-driven flow occurring in the presence of protruded heater inside a square enclosure are investigated under different thermal boundary conditions of the enclosure for two common fluids (of Prandtl numbers Pr = 0.71 and 6.9) at various Rayleigh numbers (Ra = 103–106) numerically. The study is conducted considering a single heater as well as a set of two identical heaters located symmetrically on the bottom wall of the enclosure. Results reveals that the heat transfer, energy flow and fluid flow are markedly dependent on the heater aspect ratio, Ra, Pr and thermal boundary condition. Although with the single heater symmetric trends of fluid and heat flow are observed, the strong asymmetric flow features are found in case of the double heaters for Pr = 6.9 at higher Ra. Some interesting energy and fluid flow patterns are evolved depending upon the values of heater aspect ratio, interspatial heater distance and enclosure’s boundary condition. The visualization of mass and energy transports are properly appreciated using streamfunction and heatfunction. Total fluid flow inside the enclosure is analyzed by applying a novel approach based on streamfunctions of thermally induced vortices, which is also used to formulate a new streamfunction based symmetry indicator. It is seen that, with the increase in heater height although the total flow decreases, a consistent trend of increasing heat transfer is observed. The nature of steady-state solutions for the cavity is also analyzed by gradually increasing and decreasing Ra. Symmetry breaking bifurcation has been identified for Pr = 6.9. The bifurcation characteristics changes from supercritical to subcritical bifurcation depending upon thermal boundary conditions of the enclosure.