Practical heat pump and storage integration into non-continuous processes: A hybrid approach utilizing insight based and nonlinear programming techniques

This paper focuses on industrial heat pump (HP) integration in non-continuous processes. To achieve the necessary time-wise process decoupling of the HP system, heat recovery loops (HRLs) with stratified storages are used. This design type can be modeled as a mixed integer nonlinear programming problem which often results in expensive mathematical formulations. The challenge is addressed by a practical method that combines the insight based approach of Pinch Analysis with mathematical programming techniques to give the engineer more flexibility for the application of the method and to avoid long computation times. By the use of the insight based methods, the solution space of the mathematical formulation is restricted, and thus its complexity is reduced to a nonlinear programming problem optimizing the temperature levels in the HP-HRL system. As an objective, total annual costs (TAC) of the HP-HRL system are minimized. The developed hybrid method is applied to a dairy site and compared in terms of approach temperatures, temperature lift of the HP, TAC, and greenhouse gas emissions to the existing methods. It is shown, that the hybrid method provides realistic approach temperatures in contrast to the existing insight based method

A Graphical Method for Combined Heat Pump and Indirect Heat Recovery Integration

Industrial sectors are improving their energy efficiency and increasing their share of renewables for heating and cooling demands by using lower emission technologies. One specific approach to help achieve these targets is the integration of heat pumps (HPs) in industrial processes. However, due to the temporal variation of the heating and cooling requirements in non-continuous processes, the integration of HP is challenging. In this paper, a structured method for the design of HP integration is proposed. The method implements an engineer-centred workflow that extends the concept of the Indirect Source Sink Profile (ISSP) to HP integration. For this purpose, an adapted Grand Composite Curve is derived from the ISSP. This ensures correct HP integration across the pinch while maintaining the temperature lift of the HP small. The proposed workflow is applied to a demonstration case study and a case study from industry. In both cases, the resulting system with integrated HP enables the elimination of hot utility demand and significantly reduces cold utility demands. The static paybacks of the proposed solutions are in the range of 4.5 to 5 year

Industrial heat pump integration in non-continuous processes using thermal energy storages as utility - An NLP enhancement of the graphical approach

The aim of this paper is to enhance the results of the graphical approach for Heat Pump (HP) integration in noncontinuous processes. A nonlinear programming (NLP) formulation is developed which optimizes temperature levels of condensation, evaporation, and storage temperature layers in order to further reduce total annual cost (TAC) and greenhouse gas (GHG) emissions. In addition, the NLP formulation requires low computation time given the practical approach. By its application on an AMMIX butter production of a large dairy factory, it is shown, that the temperature differences in the condenser and evaporator are reduced sharply which improves the COP of the HP from 2.2 to 3.4. As a result, the TAC can be reduced by an additional 16,721 NZD/y and the GHG emissions by an additional 29 tCO2/y in comparison to the graphical approach

The Structure and Thermal Stability of Amylose–Lipid Complexes: A Case Study on Amylose–Glycerol Monostearate

peer reviewedThree different crystalline amylose−glycerol monostearate (GMS) complexes with increasing thermal stability can be distinguished: type I, type IIa, and type IIb. All complexes consist of GMS-loaded amylose helices that pack hexagonally into lamellar habits. The complex melting points are proportional to the thickness of the lamellae and depend on the amount of water in the system. For type I complexes, SAXS experiments reveal folded amylose chains and a lamellar thickness governed by the presence of two stretched lipid molecules per amylose helix. In the conversion from type I to type IIa complexes, the short amylose chains unfold and assume a stretched conformation, which increases the number of aligned lipid molecules within the helices to four. In type IIb complexes, another pair of lipid molecules is added. The derived quantitative relation between crystal layer thickness, water content and melting point for amylose−GMS complexes also predicts the melting points of other amylose−monoacyl glycerol complexes