Newton-Raphson method applied to the time-superposed ILS for parameter estimation in Thermal Response Tests

Thermal Response Testing is now a well-known and widely-used method allowing the determination of the local thermal or geometrical properties of a Borehole Heat Exchanger (BHE), those properties being critical in the design of GSHP systems. The analysis of TRTs is an inverse problem that has commonly been solved using an approximation of the ILS solution. To do this, however, the heat rate during a TRT must be kept constant, or least be non time-correlated, during the test, which is a challenging constraint. Applying temporal superposition to the ILS model is a way to account for varying power, although it requires the use of an optimization algorithm to minimize the error between a parametrized model and experimental values.In this paper, the Newton-Raphson method is applied to the time-superposed ILS for parameter estimation in TRTs. The parameter estimation is limited to the effective thermal conductivity and the effective borehole resistance. Analytical expressions of the first and second derivatives of the objective function, chosen as the sum of quadratic differences, are proposed, allowing to readily inverse of the Hessian matrix and speed the convergence process.The method is tried for 9 different TRTs, 2 of which are reference datasets used for validation of the method (Beier et al., 2010). Differences between estimated and reference thermal conductivities are of 3.4% and 0.4% for the first and second reference TRTs, respectively. The method is shown to be stable and consistent: for each of the 9 TRTs, 11 realizations are performed with different initial values. Convergence is reached in all cases and all realizations lead to the same final values for a given TRT.The proposed convergence method is about 70% to 90% faster than the Nelder-Mead simplex and require about 8 times less iterations in average. The convergence speed varies between 0.3 to 13.6 s with an average of 3.7 s for all TRTs

Design of a laboratory borehole storage model

This paper presents the design process of a 4x4 Laboratory Borehole Storage (LABS) model through analytical and numerical analyses. This LABS is intended to generate reference Thermal Response Functions (TRFs) as well as to be a validation tool for borehole heat transfer models. The objective of this design process is to determine suitable geometrical and physical parameters for the LABS. An analytical scaling analysis is first performed and important scaling constraints are derived. In particular, it is shown that the downscaling process leads to significantly higher values for Neumann and convective boundary conditions whereas the Fourier number is invariant. A numerical model is then used to verify the scaling laws, determine the size of the LABS, as well as to evaluate the influence of top surface convection and borehole radius on generated TRFs. An adequate shape for the LABS is found to be a quarter cylinder of radius and height 1.0 m, weighing around 1.2 tonnes. Natural convection on the top boundary proves to have a significant effect on the generated TRF with deviations of at least 15%. This convection effect is proposed as an explanation for the difference observed between experimental and analytical results in Cimmino and Bernier (2015). A numerical reproduction of their test leads to a relative difference of 1.1% at the last reported time. As small borehole radii are challenging to reproduce in a LABS, the effect of the borehole radius on TRFs is investigated. It is found that Eskilson's radius correction (1987) is not fully satisfactory and a new correction method must be undertaken

Heat transfer study of enhanced additively manufactured minichannel heat exchangers

Three-dimensional (3D) printing, known as additive manufacturing, provides new opportunities for the design and fabrication of highly efficient industrial components. Given the widespread use of this technique by industries, 3D printing is no longer limited to building prototypes. Instead, small-to-medium scale production units focus on reducing the cost associated with each part. Among the various industrial components that can be developed with this manufacturing technology are heat transfer components such as heat exchangers. To this end, this study investigated the heat transfer characteristics of minichannel-based heat exchangers embedded with longitudinal vortex generators, both experimentally and numerically. Three enhanced prototypes with different vortex generator design parameters and a smooth channel as a reference case were printed with an aluminum alloy (AlSi10Mg) using direct metal laser sintering (DMLS). The rectangular minichannel had a hydraulic diameter of 2.86 mm. Distilled water was used as the test fluid, and the Reynolds number varied from 170 to 1380 (i.e., laminar flow). Prototypes were tested under two different constant heat fluxes of 15 kW m−2 and 30 kW m−2. The experimental results were verified with a commercial simulation tool, Comsol Multiphysics®, using the 3D conjugate heat transfer model. In the case of the smooth channel, the experimental results were also compared with well-known correlations in the field. The results showed that 95% and 79% of the experimental data were within 10% of the numerical simulation results and the values from the existing correlations, respectively. For the channel enhanced with the vortex generators, the numerical predictions agreed well with the experimental results. It was determined that the vortex generators can enhance the convective heat transfer up to three times with the designed parameter. The findings from this research underline the potential of additive manufacturing in the development of more sophisticated minichannel heat exchangers.The Swedish National Infrastructure for Computing (SNIC) at PDC Centre for High Performance Computing (PDC-HPC).http://www.elsevier.com/locate/hmt2021-08-13hj2021Mechanical and Aeronautical Engineerin

Swedish Teacher Conceptions of Assessment study

This project studies Swedish teacher conceptions of assessment in a repeated measurement invariance test of self-reported responses to a Swedish adaptation of the Teacher Conceptions of Assessment inventory. There is an SPSS data file, an AMOS model analysis file, and an image file of the main results. This word document is a preprint of a file currently under submission at a journal. AbstractUnderstanding teachers’ conceptions of assessment is a key objective in supporting assessment practices that lead to improved learning outcomes. Thus, inventories capable of identifying teachers assessment conceptions are important. The Teachers Conceptions of Assessment (TCoA) inventory was an early and influential measure of teacher assessment conceptions, but replication studies have shown that the model may be affected by policy and practice context. In the present study, a Swedish adaptation of the TCoA was administered twice, 18 months apart. A sample of 257 teachers were matched across the two time-points and their self-reported scores were analysed with confirmatory factor analysis and invariance testing. With good correspondence to the data, five of the nine factors in the TCoA were completely replicated and one factor was partially replicated. The model had sufficient similarity between time points to permit mean score comparisons, which were largely equivalent between times. The study indicates that the Swedish Teacher Conceptions of Assessment adaptation can be used reliably in Swedish primary and lower secondary schools as measure of teacher conceptions of the uses of assessment.</p

Cisplatin binds human copper chaperone Atox1 and promotes unfolding in vitro

Cisplatin (cisPt), Pt(NH3)2Cl2, is a cancer drug believed to kill cells via DNA binding and damage. Recent work has implied that the cellular copper (Cu) transport machinery may be involved in cisPt cell export and drug resistance. Normally, the Cu chaperone Atox1 binds Cu(I) via two cysteines and delivers the metal to metal-binding domains of ATP7B; the ATP7B domains then transfer the metal to the Golgi lumen for loading on cuproenzymes. Here, we use spectroscopic methods to test if cisPt interacts with purified Atox1 in solution in vitro. We find that cisPt binds to Atox1’s metal-binding site regardless of the presence of Cu or not: When Cu is bound to Atox1, the near-UV circular dichroism signals indicate Cu-Pt interactions. From NMR data, it is evident that cisPt binds to the folded protein. CisPt-bound Atox1 is however not stable over time and the protein begins to unfold and aggregate. The reaction rates are limited by slow cisPt dechlorination. CisPt-induced unfolding of Atox1 is specific because this effect was not observed for two unrelated proteins that also bind cisPt. Our study demonstrates that Atox1 is a candidate for cisPt drug resistance: By binding to Atox1 in the cytoplasm, cisPt transport to DNA may be blocked. In agreement with this model, cell line studies demonstrate a correlation between Atox1 expression levels, and cisplatin resistance