Sayuj Sasidharan and Pradip Dutta
This paper aims to deal with characterisation of the thermal performance of a hybrid tubular and cavity solar thermal receiver.
Abstract
Purpose
This paper aims to deal with characterisation of the thermal performance of a hybrid tubular and cavity solar thermal receiver.
Design/methodology/approach
The coupled optical-flow-thermal analysis is carried out on the proposed receiver design. Modelling is performed in two and three dimensions for estimating heat loss by natural convection for an upward-facing cavity. Heat loss obtained in two dimensions by solving coupled continuity, momentum and energy equation inside the cavity domain is compared with the loss obtained using an established Nusselt number correlation for realistic receiver performance prediction.
Findings
It is found that radiation emission from a heated cavity wall to the ambient is the dominant mode of heat loss from the receiver. The findings recommend that fluid flow path must be designed adjacent to the surface exposed to irradiation of concentrated flux to limit conduction heat loss.
Research limitations/implications
On-sun experimental tests need to be performed to validate the numerical study.
Practical implications
Numerical analysis of receivers provides guidelines for effective and efficient solar thermal receiver design.
Social implications
Pressurised air receivers designed from this method can be integrated with Brayton cycles using air or supercritical carbon-dioxide to run a turbine generating electricity using a solar heat source.
Originality/value
The present paper proposes a novel method for coupling the flux map from ray-tracing analysis and using it as a heat flux boundary condition for performing coupled flow and heat transfer analysis. This is achieved using affine transformation implemented using extrusion coupling tool from COMSOL Multiphysics software package. Cavity surface natural convection heat transfer coefficient is obtained locally based on the surface temperature distribution.
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Prodyut Chakraborty and Pradip Dutta
The purpose of this paper is to present a new numerical approach for modeling the multi‐phase flow during an alloy solidification process. In many solidification processes…
Abstract
Purpose
The purpose of this paper is to present a new numerical approach for modeling the multi‐phase flow during an alloy solidification process. In many solidification processes, advection of solid may have a dramatic effect on bulk convection field as well as on the solid front growth and hence on the macro‐segregation pattern. In the present work, a numerical model is developed to simulate directional solidification in presence of melt convection as well as solid advection in the form of sedimentation. A 2D cavity filled with hyper‐eutectic aqueous ammonium chloride solution (25 wt.% of ammonium chloride) being chilled from one of the side walls has been chosen as the model problem for the numerical simulation.
Design/methodology/approach
A fixed grid volume averaging technique has been used for solving mass, momentum, energy, and species equation while taking into account the solid phase advection and local re‐melting. Two different criteria have been identified for the solid particles in the mushy zone to be mobile. These two criteria are represented by a critical solid fraction, and a critical velocity. Based on these two criteria, the mushy zone has been subdivided into two different regions namely, an immobile coherent zone consisting of packed equiaxed crystals and a mobile non‐coherent zone where the solid crystals are able to move.
Findings
The numerical results are compared with corresponding experimental observations.
Originality/value
The solid advection velocity and source terms dealing with solid velocity have been calculated using an explicit scheme, whereas the main conservation equations are solved using an implicit scheme.
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G. Phanikumar, K. Chattopadhyay and Pradip Dutta
The transport phenomena (heat transfer, fluid flow and species distribution) are numerically modelled for the case of laser welding of dissimilar metals. The model involves…
Abstract
The transport phenomena (heat transfer, fluid flow and species distribution) are numerically modelled for the case of laser welding of dissimilar metals. The model involves convection in the weld pool along with melting and mixing. The associated metallurgical phenomenon is an extremely complex one, and the present work is a preliminary attempt to model the process after making suitable assumptions. The numerical study is performed using a pressure based finite volume technique after making appropriate modifications to the algorithm to include the associated phase change processes and dissimilarity in the metal properties. The phase change process is modelled using an enthalpy‐porosity technique, while the dissimilar metal properties are handled using appropriate mixture theories. As a case study, we have used dissimilar couples of copper‐nickel. It is observed that the weld pool shape becomes asymmetric even when the heat source is symmetrically applied on the two metals forming the couple. As the weld pool develops, the side melting earlier is found to experience more convection and better mixing. Corresponding experiments are performed using the same parameters as in the computations, showing a good qualitative agreement between the two results. A scale analysis is performed to predict the time scale of initiation of melting of each metal. The scale‐analysis predictions show a good agreement with the numerical results.
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Nilanjan Chakraborty, Suman Chakraborty and Pradip Dutta
In this paper, we present a modified k‐ε model capable of addressing turbulent weld‐pool convection in the presence of a continuously evolving phase‐change interface during a gas…
Abstract
In this paper, we present a modified k‐ε model capable of addressing turbulent weld‐pool convection in the presence of a continuously evolving phase‐change interface during a gas tungsten arc welding (GTAW) process. The phase change aspects of the present problem are addressed using a modified enthalpy‐porosity technique. The k‐ε model is suitably modified to account for the morphology of the solid‐liquid interface. The two‐dimensional mathematical model is subsequently utilised to simulate a typical GTAW process with high power, where effects of turbulent transport can actually be realised. Finally, we compare the results from turbulence modelling with the corresponding results from a laminar model, keeping all processing parameters unaltered. The above comparison enables us to analyse the effects of turbulent transport during the arc welding process.
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Anirban Bhattacharya and Pradip Dutta
In the present work, a numerical method, based on the well established enthalpy technique, is developed to simulate the growth of binary alloy equiaxed dendrites in presence of…
Abstract
Purpose
In the present work, a numerical method, based on the well established enthalpy technique, is developed to simulate the growth of binary alloy equiaxed dendrites in presence of melt convection. The paper aims to discuss these issues.
Design/methodology/approach
The principle of volume-averaging is used to formulate the governing equations (mass, momentum, energy and species conservation) which are solved using a coupled explicit-implicit method. The velocity and pressure fields are obtained using a fully implicit finite volume approach whereas the energy and species conservation equations are solved explicitly to obtain the enthalpy and solute concentration fields. As a model problem, simulation of the growth of a single crystal in a two-dimensional cavity filled with an undercooled melt is performed.
Findings
Comparison of the simulation results with available solutions obtained using level set method and the phase field method shows good agreement. The effects of melt flow on dendrite growth rate and solute distribution along the solid-liquid interface are studied. A faster growth rate of the upstream dendrite arm in case of binary alloys is observed, which can be attributed to the enhanced heat transfer due to convection as well as lower solute pile-up at the solid-liquid interface. Subsequently, the influence of thermal and solutal Peclet number and undercooling on the dendrite tip velocity is investigated.
Originality/value
As the present enthalpy based microscopic solidification model with melt convection is based on a framework similar to popularly used enthalpy models at the macroscopic scale, it lays the foundation to develop effective multiscale solidification.
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C.K. Krishnaprakas, K. Badari Narayana and Pradip Dutta
Radiative heat transfer in the laminar boundary layer flow of an absorbing, emitting and anisotropically scattering gray fluid over a flat plate, with the surface of the plate…
Abstract
Radiative heat transfer in the laminar boundary layer flow of an absorbing, emitting and anisotropically scattering gray fluid over a flat plate, with the surface of the plate reflecting radiation in diffuse‐cum‐specular fashion is analyzed. The discrete ordinates method is used to model the radiative transfer. The governing dimensionless momentum and energy equations, in the form of a partial differential system, are solved by a finite difference method. The effect of various parameters like, emittance, the degree of anisotropy in scattering, scattering albedo and the nature of surface reflection on the total heat flux from the plate to the fluid are studied and results are presented.
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The purpose of this paper is to focus on the performance analysis of Polyvinylpyrrolidone (PVP) – Chitosan composite dye transfer inhibitor (DTI) for household laundry. The…
Abstract
Purpose
The purpose of this paper is to focus on the performance analysis of Polyvinylpyrrolidone (PVP) – Chitosan composite dye transfer inhibitor (DTI) for household laundry. The developed composite DTI is tested against different commercial dyes and detergent powders normally used in the household laundry for its performance.
Design/methodology/approach
The DTI article is tested for its performance against five commercial dyes and five commercial detergent compositions. The dye re-deposition behaviour of the control fabric was measured in terms of the colour difference (ΔE) values. The influence of PVP on the washing efficiency of detergent was evaluated against tea, coffee and juice stains.
Findings
The results showed that there is an excellent performance of the developed product noted in terms of DTI performance against reactive, basic and sulfur dyes. The DTI product showed a significantly (p<0.05) less performance against acid and direct dyes. There is no significant differences noted in the stain removal efficiency of the detergent in the presence of PVP in the wash liquor (p>0.05).
Originality/value
The usage of DTI polymer in the household laundry has no significant influence on the detergents performance in terms of stain removing efficiency. The DTI polymer’s function in the wash liquor depends up on the type of polymer used, as they are sensitive to the type of detergent compositions used and the type of dyes bleeds in the wash liquor.
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Sanjay Dhamija and Reena Nayyar
After reading the case, the students shall be able to explain the concept of insider trading and differentiate between illegal insider trading and legal insider trading, business…
Abstract
Learning outcomes
After reading the case, the students shall be able to explain the concept of insider trading and differentiate between illegal insider trading and legal insider trading, business ethics, financial institutions, financial markets and accounting; to interpret the legal framework for prevention of insider trading; to identify the role and significance of the market regulator, Securities and Exchange Board of India (SEBI), in detecting financial crimes such as insider trading; to demonstrate the association between information, stock trading and stock prices within the framework of efficient markets; and to appraise the ethical dilemma in a family-owned firm, where the family members of the promoter group are alleged to have indulged in a financial crime.
Case overview/synopsis
The case revolves around allegations of insider trading against the promoter and the promoter group of the family owned and controlled firm, Lux Industries Limited. On January 24, 2022, the SEBI, the regulator of securities markets in India, accused Udit Todi, the Executive Director of Lux Industries Limited, of engaging in insider trading through a chain of 14 connected parties. Udit Todi was also the son of the Managing Director, Pradip Kumar Todi, and the nephew of the Executive Chairman, Ashok Kumar Todi. In its interim order, SEBI alleged a breach of insider trading regulations by a group of 14 connected entities that had built up long positions starting from May 21, 2021, before the quarterly financial results (Q4) and the annual results of the financial year (FY) 2021 in the equity shares of Lux Industries Limited, with its registered office in Kolkata, India, were announced. Subsequently, they squared off the long positions to make a profit of ₹29.43m. To restore the confidence of the investors, the Executive Chairman, Ashok Kumar Todi, needed to review the matter expeditiously and impartially. Taking into consideration the family ties of the accused, it was not going to be an easy task, yet, it had to be done. The case highlights the role of the regulator, SEBI, in unearthing financial frauds such as insider trading in an emerging market such as India.
Complexity academic level
Postgraduate programs in management, Executive education programs.
Supplementary materials
Teaching notes are available for educators only.
Subject code
CSS 1: Accounting and Finance
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Pradip Banerjee and Soumya G. Deb
This study seeks to examine the relationship between a firm’s effectiveness in managing working capital (WCM), as measured by the cash conversion cycle (CCC), and its exposure to…
Abstract
Purpose
This study seeks to examine the relationship between a firm’s effectiveness in managing working capital (WCM), as measured by the cash conversion cycle (CCC), and its exposure to product market competition (PMC).
Design/methodology/approach
Using 85,356 firm-year observations of 9,611 unique firms for the period 1990–2019, from the US, the baseline model assesses the CCC and PMC connection while controlling for multiple firm-level factors. Additional analyses are conducted to control for financial constraints, economic policy uncertainty, and endogeneity.
Findings
An inverse relationship is shown between PMC and CCC, indicating that firms facing increased competition tend to implement more efficient WCM strategies in order to free up scarce resources. In addition, we observe that increased PMC pushes companies to strategically adjust their credit policies, while also improving their administration of payables and inventories, resulting in improved efficiency. Our research highlights that CCC serves as a mediator between PMC and firm performance.
Research limitations/implications
This study enhances comprehension of the impact of PMC on WCM, offering practical recommendations for companies seeking to optimize their strategy in competitive settings.
Originality/value
The study provides valuable insights for managers operating in competitive markets, highlighting the significant influence of working capital on business policies as a response to competition. This study contributes to the existing literature on WCM and PMC by providing guidance to organizations on how to improve their WCM practices, maintain competitiveness, and free up scarce resources.