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Geometry development of the internal duct system of a heat pump tumble dryer based on fluid mechanic parameters from a CFD software
Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.ORCID iD: 0000-0002-3923-9807
Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
2011 (English)In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 88, no 5, p. 1596-1605Article in journal (Refereed) Published
Abstract [en]

One aspect of reducing the energy consumption of a household tumble dryer is to reduce the pressure drop of the circulating air in the internal duct system. It is, however, costly and time consuming to design several prototypes for airflow measurements. In this paper, several fluid mechanic parameters in a partial model of the internal duct system of a tumble dryer have been studied in the CFD software Comsol MultiPhysics. The purpose was to establish a numerically based design process, where the design is conducted based on visual analysis of air velocity and vorticity, and two design criteria. The geometry design was conducted by a CAD-engineer, which was the counterpart of this project. In order to enable a successful design process, it was essential to establish a strong relation between fluid parameters and design criteria in order to share knowledge effectively with the CAD engineer. Two geometry modifications, based on a standard model, were conducted on the duct. Based on the design criteria, the pressure drop and the non-uniformity coefficient of the outlet airflow, the second modification (Modification 2) represents an improvement as the pressure drop is reduced by 23% and the uniformity at the outflow section is increased by 3%.

Place, publisher, year, edition, pages
Elsevier, 2011. Vol. 88, no 5, p. 1596-1605
Keywords [en]
CFD, Tumble dryer, Fluid mechanics, Design process, Geometry design
National Category
Fluid Mechanics
Research subject
Environmental and Energy Systems
Identifiers
URN: urn:nbn:se:kau:diva-6673DOI: 10.1016/j.apenergy.2010.10.047ISI: 000288360500015OAI: oai:DiVA.org:kau-6673DiVA, id: diva2:376048
Available from: 2010-12-09 Created: 2010-12-09 Last updated: 2025-10-16Bibliographically approved
In thesis
1. CFD as a tool for analysis of complex geometry: Perspectives on time efficient simulations of interior household appliance components
Open this publication in new window or tab >>CFD as a tool for analysis of complex geometry: Perspectives on time efficient simulations of interior household appliance components
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Throughout recent years, computer based programs has been applied to solve and analyze industrial problems. One of these developed programs is the Computational Fluid Dynamics (CFD) program. The purpose of implementing CFD analysis is to solve complex flow behavior which is not possible with ordinary calculus. The extensive application of CFD in the industry is a result of improved commercial CFD codes  in terms of more advance partial differential equations (PDE) describing various physical phenomena, CAD and mesh-grid generating tools and improved graphical user interfaces (GUI). Today, CFD usage has extended to fields such as aerodynamic, chemical process engineering, biomedical engineering and drying technology.

As there is an on-going expansion of CFD usages in the industry, certain issues need to be addressed as they are frequently encountered. The general demand for simulation of larger control volumes and more advanced flow processes result in extensive requirement of computer resources. Numerous complex flow topics today require computer cluster networks which are not accessible for every company. The second issue is the implementation of commercial CFD codes in minor industrial companies is utilized as a black box based on the knowledge on fluid mechanic theory. A vital part of the simulation process is the evaluation of data through visual analysis of flow patterns, analysis on the sensitivity of the mesh grid, investigation of quantitative parameters such as pressure loss, velocity, turbulence intensity etc. Moreover, increased partnerships between industry and the academic world involving various CFD based design processes generally yields to a verbal communication interface which is a crucial step in the process given the fact of the level of dependency between both sides. The aim of this thesis is to present methods of CFD analysis based on these issues.

In paper I, a heuristically determined design process of the geometry near the front trap door of an internal duct system was achieved by implementing the CFD code COMSOL MultiPhysics as a communication tool. The design process was established by two counterparts in the project in which CFD calculations and geometry modifications were conducted separately. Two design criteria presenting the pressure drop in duct and the outflow uniformity was used to assess geometry modifications conducted by a CAD-engineer. The geometry modifications were based on visual results of the flow patterns. The geometry modifications confirmed an improvement in the geometry as the pressure drop was reduced with 23% and the uniformity was increased with 3%.

In paper II, volume-averaged equations were implemented in a tube-fin heat exchanger in order to simulate airflow. Focus was on achieving a correct volume flow rate and pressure drop (V-p) correlation. The volume averaged model (VAM) is regarded as a porous medium in which the arrangement of fins and tube bundles are replaced with volume-averaged equations. Hence, the computational time was reduced significantly for the VAM model. Moreover, experimental results of the (V-p) correlation showed good agreement with the VAM model.

Place, publisher, year, edition, pages
Karlstad: Karlstad University, 2011. p. 50
Series
Karlstad University Studies, ISSN 1403-8099 ; 2010:40
Keywords
CFD, Tumble dryer, Fluid mechanics, Design process, Heat exchanger, Comsol MultiPhysics, Volume averaged method
National Category
Fluid Mechanics
Research subject
Environmental and Energy Systems
Identifiers
urn:nbn:se:kau:diva-6687 (URN)978-91-7063-331-7 (ISBN)
Presentation
2011-02-04, 9C203, 13:15 (Swedish)
Opponent
Supervisors
Available from: 2011-02-02 Created: 2010-12-10 Last updated: 2025-10-16Bibliographically approved
2. Methods for Reducing the Complexity of Geometrical Structures Based on CFD Programming: Time Efficient Simulations Based on Volume Forces Coupled with Single and Two-phase Flow
Open this publication in new window or tab >>Methods for Reducing the Complexity of Geometrical Structures Based on CFD Programming: Time Efficient Simulations Based on Volume Forces Coupled with Single and Two-phase Flow
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Throughout recent years, computer based programs have been applied to solve and analyse industrial problems encountered global fields such as automobile design for reduction of CO2-gas, designing wind parks aimed at increasing power output etc. One of these developed programs is Computational Fluid Dynamics (CFD) which numerically solves complex flow behaviour based on computer power.

As there is an ongoing expansion of CFD usage in industry, certain issues need to be addressed as they are becoming more frequently encountered. The general demand for the simulation of larger control volumes and more advanced flow processes result in an extensive requirement of computer resources. Moreover, the implementation of commercial CFD codes in small-scaled industrial companies seems to generally be utilised as a black box based on the knowledge of fluid mechanic theory. Increased partnerships between industry and the academic world involving various CFD based design processes generally yield to a verbal communication interface, which is a crucial step in the process given the level of dependency between both sides.

Based on these notions, a method for establishing time efficient CFD-models with implementation of volume forces as sink terms in the momentum equation is presented. The internal structure, or parts of the structure, in the simulation domain is removed which reduces the geometrical complexity and along with it, computational demand.  These models are the basis of assessing the benefits of utilizing a numerical based design process in industry in which the CFD code is used as a communication tool for knowledge sharing with counterparts in different fields.

Abstract [en]

As there is an ongoing expansion of CFD usage in industry, certain issues need to be addressed as they are becoming more frequently encountered. The general demand for the simulation of larger control volumes and more advanced flow processes result in an extensive requirement of computer resources. Moreover, the implementation of commercial CFD codes in small-scaled industrial companies seems to generally be utilised as a black box based on the knowledge of fluid mechanic theory. Increased partnerships between industry and the academic world involving various CFD based design processes generally yield to a verbal communication interface, which is a crucial step in the process given the level of dependency between both sides.

Based on these notions, a method for establishing time efficient CFD-models with implementation of volume forces as sink terms in the momentum equation is presented. The internal structure, or parts of the structure, in the simulation domain is removed which reduces the geometrical complexity and along with it, computational demand.  These models are the basis of assessing the benefits of utilizing a numerical based design process in industry in which the CFD code is used as a communication tool for knowledge sharing with counterparts in different fields.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2014. p. 104
Series
Karlstad University Studies, ISSN 1403-8099 ; 2014:32
Keywords
Numerical design cycle, CFD, porous media, volume forces, heat exchanger, vacuum dewatering, time efficient simulations
National Category
Fluid Mechanics
Research subject
Environmental and Energy Systems
Identifiers
urn:nbn:se:kau:diva-31983 (URN)978-91-7063-565-6 (ISBN)
Public defence
2014-06-09, 9C 204, Universitetsgatan 2, Karlstad, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2014-05-19 Created: 2014-04-25 Last updated: 2025-10-16Bibliographically approved

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Rezk, KamalForsberg, Jan

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