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Abstract: Significant energy savings can be achieved in the pulp and paper industry through process integration. The aim of this paper was to investigate how much seasonal variations in the process influence the potential for making energy savings. The hot and warm water system in a market pulp mill has been evaluated from an energy point of view, using pinch analysis. Considerable energy-saving potential was found, 40.7MW, of which 16.5MW was in the form of steam savings. The steam savings represent 7% of the total steam consumption at the mill. New heat exchanger networks were redesigned using different approaches. The influence of seasonal variations was estimated from the calculated energy savings when monthly averages were used in the new heat exchanger networks. When seasonal variations were taken into account, the energy-saving opportunities fell by 2.5–5.0MW, depending on heat exchanger network design, compared with a steady-state scenario. Consequently, 88–94% of the theoretical energy savings could be realised. An economic evaluation indicates positive earnings from investment in a new heat exchanger network when seasonal variations were taken into account, even with low prices for the extracted steam and excess heat (5€/MWh) and with an annuity factor of 0.2. [Copyright &y& Elsevier]

This paper presents an improved semi-analytical model for the heat transfer related to a coaxial borehole heat exchanger (BHE). This model, referred to as the composite coaxial (CCx) model, is verified using results from three different thermal response tests performed on full-scale coaxial BHEs having various pipe size and material properties. The model is further used to analyze the performance and length requirements of various coaxial configurations comparing the use of a steel outer pipe to an insulated inner pipe. This comparison is made considering standard HDPE pipe sizes as the status quo, where the parameters are kept within the verified tested limit of the model. The results show, in comparison to using an insulated inner pipe, that a steel outer pipe has a greater impact on reducing the overall length requirement while maintaining system performance. [ABSTRACT FROM AUTHOR]

In the present paper, exergy loss analysis of newly designed compact heat exchanger (CHE) was experimentally investigated. For this reason, experimental system used for experimental analysis of the newly designed CHE and brazed plate heat exchanger (BPHE) were designed and constructed. Thermodynamic analysis of newly designed CHE and BPHE were also investigated. The experimental results of the CHE and BPHE are compared. Exergy loss values are calculated for each heat exchanger type. The experimental results show that similar exergy loss values were obtained. The highest exergy loss value for newly designed CHE has been obtained as about 7.6 kW, while the least exergy loss value has been obtained as about 4.65 kW for the same heat exchanger. The results of the experiments are compared and presented graphically. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the new approach of constructal theory has been employed to design shell and tube heat exchangers. Constructal theory is a new method for optimal design in engineering applications. The purpose of this paper is optimization of shell and tube heat exchangers by reduction of total cost of the exchanger using the constructal theory. The total cost of the heat exchanger is the sum of operational costs and capital costs. The overall heat transfer coefficient of the shell and tube heat exchanger is increased by the use of constructal theory. Therefore, the capital cost required for making the heat transfer surface is reduced. Moreover, the operational energy costs involving pumping in order to overcome frictional pressure loss are minimized in this method. Genetic algorithm is used to optimize the objective function which is a mathematical model for the cost of the shell and tube heat exchanger and is based on constructal theory. The results of this research represent more than 50% reduction in costs of the heat exchanger. [Copyright &y& Elsevier]

The intermediate fluid vaporizer has wide applications in the regasification of LNG (liquefied natural gas). The heat exchanger performance is one of the main contributors to the thermodynamic and cost effectiveness of the entire LNG regasification system. Within the paper, the authors discuss a new concept for a compact heat exchanger with a micro-cellular structure medium to minimize volume and mass and to increase thermal efficiency. Numerical calculations have been conducted to design a metal-foam filled plate heat exchanger and a shell-and-tube heat exchanger using published experimental correlations. The geometry of both heat exchangers was optimized using the conditions of thermolators in LNG regasification systems. The heat transfer and pressure drop performance was predicted to compare the heat exchangers. The results show that the metal-foam plate heat exchanger has the best performance at different channel heights and mass flow rates of fluid. In the optimized configurations, the metal-foam plate heat exchanger has a higher heat transfer rate and lower pressure drop than the shell-and-tube heat exchanger as the mass flow rate of natural gas is increased. [ABSTRACT FROM AUTHOR]