Assessing the feasibility of using the heat demand-outdoor temperature function for a long-term district heat demand forecast Experimental and Numerical Analysis of a Non-Newtonian Fluids Processing Pump Experimental and Numerical Analysis of a Non-Newtonian Fluids Processing Pump

District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand – outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations. Abstract Centrifugal pumps are used in many applications in which non-Newtonian fluids are involved: food processing industry, pharmaceutical and oil/gas applications. In addition to pressure and temperature, the viscosity of a non-Newtonian fluid depends on the shear rate and usually is several orders of magnitude higher than water. High values of viscosity cause a derating of pump performance with respect to water. Nowadays, pumping and mixing non-Newtonian fluids is a matter of increasing interest, but there is still lack of a detailed analysis of the fluid-dynamic phenomena occurring within these machines. A specific design process should take into account these effects in order to define the proper pump geometry, able to operate with non-Newtonian fluids with specific characteristics. Only few approaches are available for correcting the pump performance based on the Hydraulic Institute method. In this work, an experimental and numerical campaign is presented for a semi – open impeller centrifugal pump elaborating non-Newtonian fluids. An on-purpose test bench was built and used to investigate the influence on pump performance of three different non-Newtonian fluids. Each pump performance test was accompanied by the rheological characterization of the fluid, in order to detect modifications of the rheological phenomena and allow a proper Computation Fluid Dynamics (CFD) modeling. The performance of the machine handling both Newtonian and non-Newtonian fluids are highlighted in relation with the internal flow field. Abstract Centrifugal pumps are used in many applications in which non-Newtonian fluids are involved: food processing industry, pharmaceutical and oil/gas applications. In addition to pressure and temperature, the viscosity of a non-Newtonian fluid depends on the shear rate and usually is several orders of magnitude higher than water. High values of viscosity cause a derating of pump performance with respect to water. Nowadays, pumping and mixing non-Newtonian fluids is a matter of increasing interest, but there is still lack of a detailed analysis of the fluid-dynamic phenomena occurring within these machines. A specific design process should take into account these effects in order to define the proper pump geometry, able to operate with non-Newtonian fluids with specific characteristics. Only few approaches are available for correcting the pump performance based on the Hydraulic Institute method. In this work, an experimental and numerical campaign is presented for a semi – open impeller centrifugal pump elaborating non-Newtonian fluids. An on-purpose test bench was built and used to investigate the influence on pump performance of three different non-Newtonian fluids. Each pump performance test was accompanied by the rheological characterization of the fluid, in order to detect modifications of the rheological phenomena and allow a proper Computation Fluid Dynamics (CFD) modeling. The performance of the machine handling both Newtonian and non-Newtonian fluids are highlighted in relation with the internal field.