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00306 Optimization between heating load and entropy-productionrate for endoreversible absorption heat-transformers
11 Process heating, power and incineration (energy applications in industry) 06•00303 Effects of solid particle properties on heat transfer between high-temperature gas fluidized bed and immersed surface Wang, L. et al. Applied Thermal Engineering, 2004, 24, (14 15), 2145 2156. The effects of particle size, packed density, thermal conductivity and specific heat capacity on heat transfer between a high-temperature gas fluidized bed and an immersed surface are investigated. Hollowcorundum-sphere, corundum, magnesite and quartz sand particles with different diameters within the range of 0.35-1.21 mm are used. A liquefied petroleum gas fluidized bed furnace with 0.3 m x 0.3 m crosssection at hearth bottom and 0.8 m in height is used. The furnace temperature varies in the range of 990-1010°C, the immersed object is a silver sphere of 20 mm in diameter and the fluidizing velocity is changed from about 1.0U~nf (the minimum fluidizing velocity) to about 3.0Umf. The experimental results show that, for small particles, dp < 0.8 ram, the effects of thermo-physical properties of particles on heat transfer coefficient become important with particle diameter decreasing; for large particles, @>0.8 mm, the effects of the properties on heat transfer are limited; and for all particles with diameters in the range of 0.35 1.21 into, the heat transfer coefficient between the fluidized bed and the immersed surface is insensitive to particle thermal conductivity.
06•00304 Energy analysis of impulse technology: researchscale experimental papermaking trials and simulations of industrial applications Martin, A. R. et al. Applied Thermal Engineering, 2004, 24, (16), 2411 2425. The impact of impulse technology on a system-wide level has been investigated in this study for non-integrated fine paper and linerboard mills. Impulse unit data were obtained from STFI's EuroFEX research paper machine and correlations were developed in order to predict performance (dewatering, electricity consumption) under commercial operating conditions. Mill analyses were conducted for different configurations (i.e. one or two impulse units with and without web preheating) operating with roll temperatures of 200-320°C. Results show that the ingoing dryness to the dryer section can be increased within a wide span, from 7 to 27 percentage points depending upon the grade and operating parameters. Even though electricity consumption rises dramatically from the inductively heated rolls, overall fuel savings of up to 20% can be achieved with either one or two impulse units operating at 200°C (external power plant efficiency assumed to be 45%). Impulse technology appears to be neutral in terms of production costs since increases in energy costs are expected to be counterbalanced by savings in feedstock materials and enhanced product quality. Estimates show that this technology can lead to substantial reductions in dryer section sizes for new installations or alternatively enhance productivity in existing paper machines.
06/00305 Industrial thermoforming simulation of automotive fuel tanks aus tier Wiesche, S. Applied Thermal Engineering, 2004, 24, (l 6), 2391 2409. An industrial thermoforming simulation with regard to automotive plastic fuel tanks is presented including all relevant process stages. The radiative and conductive heat transfer during the reheat stage, the deformation and stress behaviour during the forming stage, and the final cooling stage are simulated. The modelling of the thermal and rheological behaviour of the involved material is investigated in greater detail. By means of experimental data it is found that modelling of the phase transition during the process is highly important for predicting correct wall thickness distributions.
06•00306 Optimization between heating load and entropyproduction rate for endoreversible absorption heattransformers Sun, F. et al. Applied Energy, 2005, 81, (4), 434~448. For an endoreversible four-heat-reservoir absorption heat-transformer cycle, for which a linear (Newtonian) heat-transfer law applies, an ecological optimization criterion is proposed for the best mode of operation of the cycle. This involves maximizing a function representing the compromise between the heating load and the entropyproduction rate. The optimal relation between the ecological criterion and the COP (coefficient of performance), the maximum ecological criterion and the corresponding COP, heating load and entropy production rate, as well as the ecological criterion and entropyproduction rate at the maximum heating load are derived using finitetime thermodynamics. Moreover, compared with the heating-load criterion, the effects of the cycle parameters on the ecological performance are studied by numerical examples. These show that achieving the maximum ecological criterion makes the entropyproduction rate decrease by 77.0% and the COP increase by 55.4% with only 27.3% heating-load losses compared with the maximum
heating-load objective. The results reflect that the ecological criterion has long-term significance for optimal design of absorption heattransformers.
06/00307 Particulate fouling in waste incinerators as influenced by the critical sticking velocity and layer porosity Abd-Elhady, M. S. ef al. Enet:gy, 2005, 30, (8), 1469 1479. Fouling of heat transfer surfaces introduces a major uncertainty into the design and operation of heat exchange equipment. Fouling layers as observed on the tube bundles of the economizer in a Dutch waste incinerator were thin and powdery. The fouling layer showed an asymptotic growth rate with a levelling off increase of the thickness. In this study, the influence of the critical sticking velocity on the growth rate of particulate fouling layers is described. The critical sticking velocity of an incident particle hitting a powdery layer is defined as the maximum impact speed at which the particle will stick to the layer. Since the critical sticking velocity is a key parameter in the deposition mechanism, a well-defined experimental set-up has been built to assign it. Experimental results showed that the critical sticking velocity increases with the porosity of the fouling layer. Literature shows that the porosity of a thin sintered powdery layer changes with the layer thickness. Based on the experimental results and the variation of porosity with thickness for a thin sintered powdery fouling layers, a correlation is developed which shows that the sticking velocity decreases exponentially as the fouling layer thickness increases. Therefore, fewer particles are likely to stick as the fouling layer builds up and consequently the deposition rate decreases. The change in the critical sticking velocity as the fouling layer builds up contributes to the explanation of the asymptotic growth of particulate fouling layers on the tube bundle of waste incinerators.
06•00308 Performance effects of combined cycle power plant with variable condenser pressure and loading Chuang, C. C. and Sue, D.-C. Enet:gy, 2005, 30, (10), 1793 1801. Utility power producers are being driven by the inherently high efficiency and attractive installed cost of Combined Cycle Power Plants (CCPP) to consider them as the dominant choice for least-cost power. However, in a CCPP the power capability is significantly affected by the ambient temperature, condenser pressure and power demand. In the Power Purchase Agreements (PPA) written in Taiwan, the capacity payment is based on the guaranteed power output during the operating period. Therefore, operating the CCPP at the highest performance and maintaining the guaranteed or contractual power output are important factors to get the full capacity and energy payments from the power purchaser and reduce the fuel and operating costs for the power producer.
06•00309 Review of polymer compact heat exchangers, with special emphasis on a polymer film unit Zaheed, L. and Jachuck, R. J. J. Applied Thermal Engineering, 2004, 24, (16),2323 2358. This paper comprises of a general review on polymer compact heat exchangers (PCHEs). The first part outlines the types of polymers used and their respective characteristics. The second part presents the relative merits and the current PCHEs available in process industries. Following this, the recent advances in the field are addressed and finally, their future applications are discussed. In this paper, the types of polymers that can be used, as an alternative material of construction to metals in heat exchangers have been listed out. The relative merits of using polymers over metals are shown through a quantitative comparison, between PVDF and Hastelloy heat exchangers. When incorporating the same tube dimensions, thickness and fluid film coefficients, significant cost savings can be achieved using the PVDF exchanger. The descriptions of the three main categories of polymer compact heat exchangers currently available in industry are then provided to some detail. Following this, the polymer film compact heat exchanger (PFCHE) design is introduced to address the disadvantages of both metallic and present polymer heat exchangers. Notable design aspects of the unit are the use of thin (100 ~tm) polymer films to address the thermal conductivity deficiency and the adoption of laminar flows to deal with high-pressure drops. In addition, the presence of corrugations on the films promotes better fluid mixing, which increases the thermal performance of the unit. Due to its excellent thermal, chemical and mechanical stability, PEEK (poly ether ether ketone) is adopted in the PFCHE design. The benefits of the PFCHE design aspects (thin films, corrugations, narrow channels and developing laminar flow) are then highlighted. The paper concludes with a listing of the potential applications for the PFCHE in the process industries, based on the incentive provided by available polymer exchanger designs, particularly those incorporating thin polymer films.
Fuel and Energy Abstracts
January 2006
43
06•00304 Energy analysis of impulse technology: researchscale experimental papermaking trials and simulations of industrial applications Martin, A. R. et al. Applied Thermal Engineering, 2004, 24, (16), 2411 2425. The impact of impulse technology on a system-wide level has been investigated in this study for non-integrated fine paper and linerboard mills. Impulse unit data were obtained from STFI's EuroFEX research paper machine and correlations were developed in order to predict performance (dewatering, electricity consumption) under commercial operating conditions. Mill analyses were conducted for different configurations (i.e. one or two impulse units with and without web preheating) operating with roll temperatures of 200-320°C. Results show that the ingoing dryness to the dryer section can be increased within a wide span, from 7 to 27 percentage points depending upon the grade and operating parameters. Even though electricity consumption rises dramatically from the inductively heated rolls, overall fuel savings of up to 20% can be achieved with either one or two impulse units operating at 200°C (external power plant efficiency assumed to be 45%). Impulse technology appears to be neutral in terms of production costs since increases in energy costs are expected to be counterbalanced by savings in feedstock materials and enhanced product quality. Estimates show that this technology can lead to substantial reductions in dryer section sizes for new installations or alternatively enhance productivity in existing paper machines.
06/00305 Industrial thermoforming simulation of automotive fuel tanks aus tier Wiesche, S. Applied Thermal Engineering, 2004, 24, (l 6), 2391 2409. An industrial thermoforming simulation with regard to automotive plastic fuel tanks is presented including all relevant process stages. The radiative and conductive heat transfer during the reheat stage, the deformation and stress behaviour during the forming stage, and the final cooling stage are simulated. The modelling of the thermal and rheological behaviour of the involved material is investigated in greater detail. By means of experimental data it is found that modelling of the phase transition during the process is highly important for predicting correct wall thickness distributions.
06•00306 Optimization between heating load and entropyproduction rate for endoreversible absorption heattransformers Sun, F. et al. Applied Energy, 2005, 81, (4), 434~448. For an endoreversible four-heat-reservoir absorption heat-transformer cycle, for which a linear (Newtonian) heat-transfer law applies, an ecological optimization criterion is proposed for the best mode of operation of the cycle. This involves maximizing a function representing the compromise between the heating load and the entropyproduction rate. The optimal relation between the ecological criterion and the COP (coefficient of performance), the maximum ecological criterion and the corresponding COP, heating load and entropy production rate, as well as the ecological criterion and entropyproduction rate at the maximum heating load are derived using finitetime thermodynamics. Moreover, compared with the heating-load criterion, the effects of the cycle parameters on the ecological performance are studied by numerical examples. These show that achieving the maximum ecological criterion makes the entropyproduction rate decrease by 77.0% and the COP increase by 55.4% with only 27.3% heating-load losses compared with the maximum
heating-load objective. The results reflect that the ecological criterion has long-term significance for optimal design of absorption heattransformers.
06/00307 Particulate fouling in waste incinerators as influenced by the critical sticking velocity and layer porosity Abd-Elhady, M. S. ef al. Enet:gy, 2005, 30, (8), 1469 1479. Fouling of heat transfer surfaces introduces a major uncertainty into the design and operation of heat exchange equipment. Fouling layers as observed on the tube bundles of the economizer in a Dutch waste incinerator were thin and powdery. The fouling layer showed an asymptotic growth rate with a levelling off increase of the thickness. In this study, the influence of the critical sticking velocity on the growth rate of particulate fouling layers is described. The critical sticking velocity of an incident particle hitting a powdery layer is defined as the maximum impact speed at which the particle will stick to the layer. Since the critical sticking velocity is a key parameter in the deposition mechanism, a well-defined experimental set-up has been built to assign it. Experimental results showed that the critical sticking velocity increases with the porosity of the fouling layer. Literature shows that the porosity of a thin sintered powdery layer changes with the layer thickness. Based on the experimental results and the variation of porosity with thickness for a thin sintered powdery fouling layers, a correlation is developed which shows that the sticking velocity decreases exponentially as the fouling layer thickness increases. Therefore, fewer particles are likely to stick as the fouling layer builds up and consequently the deposition rate decreases. The change in the critical sticking velocity as the fouling layer builds up contributes to the explanation of the asymptotic growth of particulate fouling layers on the tube bundle of waste incinerators.
06•00308 Performance effects of combined cycle power plant with variable condenser pressure and loading Chuang, C. C. and Sue, D.-C. Enet:gy, 2005, 30, (10), 1793 1801. Utility power producers are being driven by the inherently high efficiency and attractive installed cost of Combined Cycle Power Plants (CCPP) to consider them as the dominant choice for least-cost power. However, in a CCPP the power capability is significantly affected by the ambient temperature, condenser pressure and power demand. In the Power Purchase Agreements (PPA) written in Taiwan, the capacity payment is based on the guaranteed power output during the operating period. Therefore, operating the CCPP at the highest performance and maintaining the guaranteed or contractual power output are important factors to get the full capacity and energy payments from the power purchaser and reduce the fuel and operating costs for the power producer.
06•00309 Review of polymer compact heat exchangers, with special emphasis on a polymer film unit Zaheed, L. and Jachuck, R. J. J. Applied Thermal Engineering, 2004, 24, (16),2323 2358. This paper comprises of a general review on polymer compact heat exchangers (PCHEs). The first part outlines the types of polymers used and their respective characteristics. The second part presents the relative merits and the current PCHEs available in process industries. Following this, the recent advances in the field are addressed and finally, their future applications are discussed. In this paper, the types of polymers that can be used, as an alternative material of construction to metals in heat exchangers have been listed out. The relative merits of using polymers over metals are shown through a quantitative comparison, between PVDF and Hastelloy heat exchangers. When incorporating the same tube dimensions, thickness and fluid film coefficients, significant cost savings can be achieved using the PVDF exchanger. The descriptions of the three main categories of polymer compact heat exchangers currently available in industry are then provided to some detail. Following this, the polymer film compact heat exchanger (PFCHE) design is introduced to address the disadvantages of both metallic and present polymer heat exchangers. Notable design aspects of the unit are the use of thin (100 ~tm) polymer films to address the thermal conductivity deficiency and the adoption of laminar flows to deal with high-pressure drops. In addition, the presence of corrugations on the films promotes better fluid mixing, which increases the thermal performance of the unit. Due to its excellent thermal, chemical and mechanical stability, PEEK (poly ether ether ketone) is adopted in the PFCHE design. The benefits of the PFCHE design aspects (thin films, corrugations, narrow channels and developing laminar flow) are then highlighted. The paper concludes with a listing of the potential applications for the PFCHE in the process industries, based on the incentive provided by available polymer exchanger designs, particularly those incorporating thin polymer films.
Fuel and Energy Abstracts
January 2006
43