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The pulp and paper industry is highly energy-intensive. In mills that use chemical pulping, roughly half of the higher heating value of the cellulosic material used to manufacture the product typically is incinerated to generate steam and electricity that is needed to run the processes. Additional energy, much of it non-renewable, needs to be purchased. This review considers publications describing steps that pulp and paper facilities can take to operate more efficiently. Savings can be achieved, for instance, by minimizing unnecessary losses in exergy, which can be defined as the energy content relative to a standard ambient condition. Throughout the long series of unit operations comprising the conversion of wood material to sheets of paper, there are large opportunities to more closely approach a hypothetical ideal performance by following established best-practices.

Abstract: This study considers different alternative uses of secondary heat in a mechanical pulp and paper mill. The considered alternatives are (1) three different heat exchanger network retrofits, (2) drying of bark, (3) drying of primary and activated sludge and (4) drying of both bark and sludge. The data has been gathered from an operating mill and a simulation model has been built to examine the mill-wide effects of the proposed changes. Targets for steam and cooling water use, used in the heat exchanger network retrofits, have been evaluated using pinch analysis. The amount of available secondary heat found in the pinch analysis can be used in drying of bark or sludge. Sludge is typically burned together with mill fuel in the bark boiler of a power plant to deliver heat and electricity to the mill. These wood-based biofuels typically consist of 50%w.b. water, which will evaporate and consume some of the fuel''s energy content during combustion. Fuel drying is a way to increase the heating value of fuels and to increase the energy efficiency of heat and power production. The utilisation of low-temperature secondary heat in the drying may reduce the need for fuels and primary energy in the mill. The different ways of using the secondary heat have different effects on primary fuel consumption and electricity production. Therefore the different results are compared using the reduction of CO2 emissions as a common criterion. The results show that all the considered alternatives have great energy-saving potential up to 8MW steam use in winter and 6MW in summer time. [Copyright &y& Elsevier]

Membrane heat exchangers were used for moisture and heat recovery from a hot and humid natural gas stream in indirect contact with an air stream. A plate membrane module with spiral channels on each side was designed to configure gas and air streams in co-current and counter-current flow. Two types of membranes, a commercial kraft paper, and a laboratory-made thin-film composite membrane, were used as the module core. The thermal efficiency and the water recovery from the humid gas were calculated and compared under different operating conditions. At a unit flow ratio of air/gas, the greatest effectiveness was achieved at a methane flow of 100 cm3/min, but water recovery increased at higher gas flows. For the counterflow configuration, an air/methane flow ratio of 2 was sufficient to achieve the highest total effectiveness and water recovery; however, larger air/gas ratios were beneficial to improve heat and moisture transfer for the co-current configuration. The highest water recovery by the kraft paper and composite membrane was achieved (approximately 15 mgH 2 O/cm2.h) for the input gas with the highest humidity. The dehumidification performance of kraft paper as a porous and hydrophilic membrane was slightly better than that of the composite membrane containing a dense hydrophilic polymer thin film in most cases. A relatively low heat transfer coefficient was found for the module, which was increased by using higher gas flow rates at higher humidity conditions. [Display omitted] • Use of a flat-plate spiral-channeled membrane heat exchanger for methane dehumidification. • Synthesis of a thin-film composite membrane for comparison with commercial kraft paper. • Investigation of effects of operating parameters on total effectiveness and water recovery. • Obtaining the best air/methane ratio in co-current and counter-current configurations. • Slightly better performance of kraft paper than composite membrane in dehumidification. [ABSTRACT FROM AUTHOR]

In kraft paper mills, supersonic steam jets are used to remove deposits that build up on the heat exchanger tubes in the recovery boiler. In this study, the fracture toughness KC and work of fracture, WF, of simulated boiler deposits were measured at temperatures up to 500 °C to determine the optimal conditions for deposit removal. The model deposits experienced an important brittle to ductile transition at ~450 °C. Above this temperature, ductile deposits required lower peak force, but four times more energy to fracture when compared to those tested at lower temperatures. The transition was clear in scanning electron micrographs of the fracture surfaces. The findings have significant implications for mills wishing to optimize sootblower performance. [ABSTRACT FROM AUTHOR]

Abstract: The success of any process improvement study depends on the quality of the available data and the way in which the plant-specific characteristics are incorporated in the applied conceptual models; in the context of process integration studies these issues are directly related to the rules followed during the data extraction stage. Improving energy efficiency in a pulp and paper Kraft mill requires the identification of the most promising heat recovery network retrofit projects. In a retrofit analysis using pinch technology/process integration methods, only the process streams associated to the existing heat exchangers and some outlet streams (such as wastewater/effluent streams and vents) with high potential for heat recovery are usually included, while the energy exchanged through non-isothermal stream mixing (NIM) or direct heat transfer (DHT) is often assumed fixed and is not considered in the analysis. Relaxing this assumption requires extracting more data to represent the DHT design configuration that exists in the plant. However, different data extraction options can be considered to represent the DHT configuration depending on the associated process/operation constraints. This work describes a systematic procedure to extract and analyse the impacts of DHT on the overall energy efficiency of a Kraft process with a specific focus on mixing along the pulp line and in water tanks. [Copyright &y& Elsevier]

This work presents a numerical model for the simulation of package sealing in industrial machines for beverage packaging. The simulations are aimed at the prediction of the temperature field in all the layers of the polylaminate material composing the package. The package sealing is in fact carried out by means of thermal welding. Thus, accurate predictions of the temperatures following the package heating via hot air jet and right before the folding flaps are pressed together is paramount to in turn predict sealing success. The heat equation is solved in the package volume by means of a plate FEM formulation in which arbitrary order Lagrangian shape function are used for both the longitudinal and the normal discretization. The resulting semi-discretized equations are time advanced by means of an Implicit Euler scheme with constant time step. The solution of the system is complemented by forward sensitivity computation to obtain, at each time step, quantitative assessment of the effect of process parameters variations on the temperature output. The numerical results are compared to experimental measurements so as to validate the developed simulation tool. The results obtained suggest that the solver is able to reproduce with satisfactory accuracy the experimental temperature field evolution in the portion of the package interested by the thermal welding. [ABSTRACT FROM AUTHOR]

The current discussion is presented to increase the awareness among the readers of the journal Thermal Science. Comments are presented in particular on the paper by Hayat et al. [1] where the authors investigated effect of non-linear radiative flow of third grade fluid and temperature dependent heat source with chemical aspects. The current discussion concerns some questionable results included in the aforementioned paper. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a literature review of thermal comfort. Both rational and adaptive thermal comfort approaches are presented. An overview of the human body thermoregulatory system as well as the mathematical modelling of heat exchanged between human body and its environment in the situations of both awaked and sleeping people is presented. [Copyright &y& Elsevier]

Purpose – This paper deals with the identification and diagnosis of operational variability in chemical processes, which is a common problem in mills but little explored in literature. The Cross-Industry Standard Process for Data Mining (CRISP-DM) is a widely used approach in problem solving. The purpose of this paper is to: first, contribute to the body of knowledge on applying CRISP-DM in a pulp mill production process and the special issues that need to be considered in this context. Exact amounts of a cost increase due to variation in pulp production have not been reported previously. Second, to quantify the cost of variation. Design/methodology/approach – In the case studied, the variation in a pulp mill batch cooking process had increased. In order to identify the causes of variation, CRISP-DM was applied. Findings – The cycle of variation was identified and found to be related to the batch cooking process cycle time. By using information from this analysis it was possible to detect otherwise unobserved defective steam nozzles. The defective equipment was repaired and improved. Further improvement was achieved when the fouling of a heat exchanger was found by analysis to be the root cause of long-term variability parameters. By applying CRISP-DM, equipment defects and fouling were identified as the root causes of the higher manufacturing costs due to increased variation were detected and estimated. The Taguchi loss function is a possible tool for estimating the cost of variation in pulp manufacturing. Originality/value – This paper provides new knowledge in the context of implementing CRISP-DM and the Taguchi loss function in the pulp and paper manufacturing process. [ABSTRACT FROM AUTHOR]

Operation of the total heat exchangers (THXs) discussed in this article is based on thin fibrous paper, permeable to moisture but highly impermeable to air, capable of recovering both sensible and latent heat from air. By exchanging sensible and latent heat between fresh air and exhaust air, THXs show great energy-saving potential when fresh air is required for IAQ purposes in a conditioned space. Due to the fibrous permeability of the functional paper, air leakage may occur and, when significant, must be accounted for in evaluating the performance of THXs. In this study, a concept of effective fresh air efficiency defined on the basis of per-unit-effective-fresh-air is proposed and the leakage effect on efficiency is examined with experiments. Both heat and mass transfer effectiveness of THXs were compared with that of the Japan Refrigeration and Air Conditioning Industry Association standards (JRAIA). The results showed that the energy-saving index, or THX effectiveness, of JRA overestimated the performance of THXs if air leakage was present. [ABSTRACT FROM AUTHOR]

Experimental and analytical investigation was carried out to show the effect of surface tension on the heat transfer coefficient of gas flow inside micropipe heat exchangers during the condensation process. An empirical correlation was formulated for the coefficient of the convective heat transfer. A comprehensive comparison between the experimental results with published correlations in the literature and that obtained by the developed correlation was conducted. The results showed that the predicted heat transfer coefficient of the proposed correlation was closer to the experimental results than any other correlation, a finding related to the consideration of the surface tension. [ABSTRACT FROM AUTHOR]

SUMMARY The present study deals with a comprehensive thermodynamic modeling of a combined heat and power (CHP) system in a paper mill, which provides 50 MW of electric power and 100 ton h−1 saturated steam at 13 bars. This CHP plant is composed of air compressor, combustion chamber (CC), Air Preheater, Gas Turbine (GT) and a Heat Recovery Heat Exchanger. The design parameters of this cycle are compressor pressure ratio ( rAC), compressor isentropic efficiency ( ηAC), GT isentropic efficiency ( ηGT), CC inlet temperature ( T3), and turbine inlet temperature ( T4). In the multi-objective optimization three objective functions, including CHP exergy efficiency, total cost rate of the system products, and CO2 emission of the whole plant, are considered. The exergoenvironmental objective function is minimized whereas power plant exergy efficiency is maximized using a Genetic algorithm. To have a good insight into this study, a sensitivity analysis of the results to the interest rate as well as fuel cost is performed. The results show that at the lower exergetic efficiency, in which the weight of exergoenvironmental objective is higher, the sensitivity of the optimal solutions to the fuel cost is much higher than the location of the Pareto Frontier with the lower weight of exergoenvironmental objective. In addition, with increasing exergy efficiency, the purchase cost of equipment in the plant is increased as the cost rate of the plant increases. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The thermal performance of a Z shape enthalpy heat exchanger utilising 70 gsm Kraft paper as the heat and moisture transfer surface has been investigated. Effects of different inlet air humidity ratio conditions on the heat exchanger effectiveness and on the energy recovered by the heat exchanger have been the main focus of this investigation. A typical air conditioning cooling coil which incorporates an enthalpy heat exchanger has been modelled for tropical climate. Under test conditions, results have shown that latent effectiveness and the moisture resistance coefficient have strong dependency on the inlet air humidity ratio. Moreover, the latent effectiveness has been found to be strongly dependent on the moisture resistance coefficient rather than the convective mass transfer coefficient. Finally, annual energy analysis for Singapore weather conditions have also shown that energy recovered under variable inlet air conditions is 15% less than that recovered under constant inlet air conditions for the same heat exchanger. [ABSTRACT FROM AUTHOR]

This paper introduces three novel approaches to size geothermal energy piles in a MILP, offering fresh perspectives and potential solutions. The research overlooks MILP models that incorporate the sizing of a geothermal borefield. Therefore, this paper presents a new model utilizing a g-function model to regulate the power limits. Geothermal energy is an essential renewable source, particularly for heating and cooling. Complex energy systems, with their diverse sources of heating and cooling and intricate interactions, are crucial for a climate-neutral energy system. This work significantly contributes to the integration of geothermal energy as a vital energy source into the modelling of such complex systems. Borehole heat exchangers help generate heat in low-temperature energy systems. However, optimizing these exchangers using mixed-integer-linear programming (MILP), which only allows for linear equations, is complex. The current research only uses R-C, reservoir, or g-function models for pre-sized borefields. As a result, borehole heat exchangers are often represented by linear factors such as 50 W/m for extraction or injection limits. A breakthrough in the accuracy of borehole heat exchanger sizing has been achieved with the development of a new model, which has been rigorously compared to two simpler models. The geothermal system was configured for three energy systems with varying ground and bore field parameters. The results were then compared with existing geothermal system tools. The new model provides more accurate depth sizing with an error of less than 5 % compared to simpler models with an error higher than 50 %, although it requires more calculation time. The new model can lead to more accurate borefield sizing in MILP applications to optimize energy systems. This new model is especially beneficial for large-scale projects that are highly dependent on borefield size. [ABSTRACT FROM AUTHOR]

In order to understand the application of frost measurement of air source heat pump heat exchanger, a research on frost measurement of air source heat pump heat exchanger based on image recognition processing technology is put forward. In this paper, the scheme design of defrosting control system based on image processing technology is introduced, and the frost degree coefficient of outdoor heat exchanger fin surface is introduced to characterize the frost degree of fin surface. Secondly, the experimental environment room was built, and the conventional defrosting control method of the existing heat pump unit was tested on the spot. It was found that in the air temperature of -6~0 °C and the air relative humidity of 86~92%, the unit appeared the phenomenon of "defrosting in time" and "defrosting without frost". Finally, the change of frost layer on the surface of the outdoor heat exchanger fin during defrosting is analyzed, and the coefficient of frost degree on the surface of the fin is calculated and analyzed. At the beginning of defrosting, due to the large degree of frost, the P-value of the frost degree coefficient on the surface of the fin is close to 1, when the defrosting is carried out for 125 seconds, the P-value of the frost degree coefficient on the surface of the fin decreases sharply to 0.09, when the defrosting is completed, the P-value of the frost degree coefficient on the surface of the outdoor heat exchanger is maintained at about 0.04. The defrosting control method of air source heat pump based on image processing technology is proposed in this paper, and its technical feasibility and effect are verified by experimental tests, which lays a foundation for future popularization and application. [ABSTRACT FROM AUTHOR]

The paper explores the application of Wilson plot method, and its modifications, as an alternative approach for determining convective heat transfer coefficients in heat exchangers with complex geometries. For achieving the delicate balance, one needs to introduce heat transfer augmentation techniques in devices, which results in intricate geometries of heat exchanger. For such geometries of heat exchanger, correlations are not available to estimate convective heat transfer coefficients. The Wilson plot method provides a robust tool for deriving correlation equations based on experimental data. The paper discusses the implementation of the Wilson plot and modified Wilson plot methods to establish correlations for tube-in-tube type heat exchangers with wire mesh inserts, and results are obtained for both methods. It is found that modified Wilson plot method provides correlation with great accuracy in the range of 94 to 97%. Furthermore, the paper presents the development of a computational tool using VB.net, designed to facilitate the iterative calculations required for Wilson plot methods. The paper also describes a roadmap for the proficient application of Wilson plot method and its modification in heat exchanger analysis. [ABSTRACT FROM AUTHOR]

The article reports that Fraser Papers Inc. hired ForEverGreen Energy Inc. to upgrade a pulp mill in Thurso, Quebec with a thermal power producing heat exchange device. The unit is expected to reduce energy costs as well as sulfur dioxide and nitrous oxide emissions. Jean-Pierre Benoit, the plant's general manager, is quoted discussing the company's commitment to environmental awareness. It is noted that the heat exchange unit is expected to reduce a quantity of emissions equivalent to that produced by 2000 cars.

An introduction is presented in which the editor discusses various reports within the issue on topics including the thermal design of plate fin heat exchangers, studies on dropwise condensation, and the modification of Wilson Plots.

An introduction to the journal is presented on topics including heat transfer and fluid flow processes in practical engineering applications; optimization of heat exchangers and power boilers; and analysis of thermal engineering applications.

Pulsating Heat Pipe (PHP) is an emerging efficient heat transfer device, that transfers heat passively through oscillating motions of liquid slugs and vapor plugs within the device. PHP is of high effective thermal conductivity with great potential in heat transfer management for various applications. The objective of this review paper is to summarize and analyse the applications of PHP in various fields that have been reported in the open literature, emphasizing on studies reported in past half decade. The thermo-hydraulic behaviour of PHP is influenced by numerous geometric and operational parameters, which are discussed in detail in the first part of the paper. The thermal performance of the PHP under rotation condition, which is seldom discussed in previous review articles, is also discussed. These parameters act individually and in tandem to alter the performance of PHP, which makes its prediction extremely difficult. However, the benefit of numerous influencing parameters is that they can be altered to make PHP suitable for various applications. These highly variable configurations make PHP suitable for applications such as the transfer of absorbed solar energy to the location of interest, waste heat recovery, thermal management of electric vehicle batteries, fuel cells, cooling of electronic components etc. PHPs are recently being studied for applications in cryogenics and cooling of cutting tools in the machining process also. In addition, novel applications of PHP such as high-performance fins for heat exchangers, cooling of building roofs etc. are also being reported. All these applications of PHP reported in the open literature are reviewed and summarized in the present article. [ABSTRACT FROM AUTHOR]

Boiling heat transfer can be enhanced when the heater's surface morphology is altered. The paper discusses the use of the laser beam to produce efficient heat exchangers. Two types of samples were investigated with distilled water and ethyl alcohol as boiling agents. The specimens differed with the height of the microfins: 0.19 mm and 0.89 mm. It was observed that both of them enhanced boiling heat transfer in comparison to the smooth reference surface. However, the sample with higher microfins performed better, especially in the region of low temperature differences, where the heat flux was about three times higher than in the case of the smaller microfins. The comparison of the experimental data with selected models of boiling heat transfer revealed significant differences with regard to the heat flux. The laser-made samples dissipated larger heat fluxes than it could be anticipated according to the models. It might be linked with high surface roughness of the area between the microfins, generated as a result of the laser beam interaction with the surface. [ABSTRACT FROM AUTHOR]