High temperature heat pump using HFO and HCFO refrigerants - System design, simulation, and first experimental results

High temperature heat pumps (HTHPs) with heat sink temperatures in the range of 100 to 160°C are expected to become increasingly commercialized in the coming years. Major applications have been identified, particularly in the food, paper, metal and chemical industries, especially in drying, sterilization, evaporation, and steam generation processes. With the intensification of the F-gas regulations, only refrigerants with low GWP may be used in the near future. Replacement fluids for the currently applied hydrofluorocarbons (HFCs) R245fa and R365mfc are required. The actual research gap in the field of HTHPs is to extend the limits of efficiency and heat sink temperature to higher values, while using environmentally friendly refrigerants. Natural refrigerants such as water (R718) or hydrocarbons (e.g. R601 or R600) are promising candidates. However, special heat pump cycle designs with multi-stage recompression or sophisticated safety measures against flammability are needed, which can increase system costs. Various hydrofluoroolefins (HFOs) and hydrochlorofluoroolefins (HCFOs) have recently been developed, which exhibit very low GWPs, are non-flammable and show potential for use at high temperatures (i.e. their critical temperatures are above 150°C). The thermodynamic properties of these fluids allow subcritical heat pump operation at condensation temperatures in the range of 100 to 160°C. This paper investigates the environmentally friendly HFOs R1336mzz(Z) and R1234ze(Z) and the HCFOs R1233zd(E) and R1224yd(Z) and compares the coefficient of performance (COP) and the volumetric heating capacity (VHC) with the refrigerants R365mfc and R245fa at different condensation temperatures and temperature lifts. Based on simulations and literature findings, a single-stage HTHP with internal heat exchanger (IHX) has been designed and built to test the performance of various refrigerants and high-viscosity oils. The established laboratory scale HTHP provides 10 kW heating capacity and heat sink temperatures of 80 to 150°C. The system operates with a variable-speed reciprocating compressor and has an oil separator installed on the discharge side of the compressor. An IHX is used to ensure adequate superheating control. The system design, theoretical simulations and first experimental test results with R1233zd(E) are presented

Examination of the neural basis of psychotic-like experiences in adolescence during processing of emotional faces

Contemporary theories propose that dysregulation of emotional perception is involved in the aetiology of psychosis. 298 healthy adolescents were assessed at age 14- and 19-years using fMRI while performing a facial emotion task. Psychotic-like experiences (PLEs) were assessed with the CAPE-42 questionnaire at age 19. The high PLEs group at age 19 years exhibited an enhanced response in right insular cortex and decreased response in right prefrontal, right parahippocampal and left striatal regions; also, a gradient of decreasing response to emotional faces with age, from 14 to 19 years, in the right parahippocampal region and left insular cortical area. The right insula demonstrated an increasing response to emotional faces with increasing age in the low PLEs group, and a decreasing response over time in the high PLEs group. The change in parahippocampal/amygdala and insula responses during the perception of emotional faces in adolescents with high PLEs between the ages of 14 and 19 suggests a potential ‘aberrant’ neurodevelopmental trajectory for critical limbic areas. Our findings emphasize the role of the frontal and limbic areas in the aetiology of psychotic symptoms, in subjects without the illness phenotype and the confounds introduced by antipsychotic medication

Decentralized DHW production from exhaust air in the bathroom prewall

In urban multifamily houses, decentralized DHW systems using gas or electric boilers are still widely used. Their replacement with renewable energy sources is difficult and generally needs centralized DHW systems with a circulation system that ensures comfort and hygiene at the price of elevated heat losses. A consortium of three academic and one industry partner developed a decentralized DHW system, which uses the residual heat from the exhaust air of a controlled ventilation unit as energy source for a micro heat pump. The entire system, including ventilation unit, heat pump, and storage tank fits into the bathroom prewall and produces hot water for one apartment. This contribution gives an overview of the system and focusses on the development of the flat storage tank that fits into the prewall space of less than 30 cm width

High temperature heat pump using HFO and HCFO refrigerants – system design and experimental results

High temperature heat pumps (HTHP) with heat sink temperatures of 100 to 160 °C will increasingly become commercialized in the coming years, especially for industrial drying, sterilization and evaporation processes. In particular, the HFO R1336mzz(Z) and the HCFOs R1233zd(E) & R1224yd(Z) are low GWP replacement refrigerants for R245fa and R365mfc. This study examines the experimental performance of R1336mzz(Z) and R1233zd(E) in a laboratory HTHP with 5 to 10 kW heating capacity. The developed heat pump is single-stage, operates with a variable speed piston compressor, and contains a continuously adjustable internal heat exchanger (IHX) for superheating control. The performance data were measured at 30, 50, and 70 K temperature lift (40 to 80°C heat source, 80 to 150°C heat sink). At W60/W110, the experimental results with R1233zd(E) showed a COP of 2.8 (basic cycle) and 3.1 with IHX integration (+15%). For R1336mzz(Z) a COP of 2.4 and 3.0 was reached (+24%). By increasing the heat sink temperature glide from 5 to 30 K, a further 15% COP increase was achieved

Overeducation and the Skills of UK Graduates

During the early 1990s the proportion of a cohort entering higher education in the UK doubled over a short period of time. The paper investigates the effect of the expansion on graduates’ early labour market attainment, focusing on overeducation. We define overeducation by combining occupation codes and a self-reported measure for the appropriateness of the match between qualification and the job. We therefore define three groups of graduates: matched, apparently overeducated and genuinely overeducated. This measure is well correlated with alternative definitions of overeducation. Comparing pre- and post-expansion cohorts of graduates, we find with this measure that the proportion of overeducated graduates has doubled, even though overeducation wage penalties have remained stable. We do not find that type of institution affects the probability of genuine overeducation. Apparently overeducated graduates are mostly indistinguishable from matched graduates, whereas genuinely overeducated graduates principally lack non-academic skills and suffer a large wage penalty. Individual unobserved heterogeneity differs between the three groups of graduates but controlling for it does not alter these conclusions

Examination of the neural basis of psychotic-like experiences in adolescenceduring processing of emotional faces

Contemporary theories propose that dysregulation of emotional perception is involved in the aetiology of psychosis. 298 healthy adolescents were assessed at age 14- and 19-years using fMRI while performing a facial emotion task. Psychotic-like experiences (PLEs) were assessed with the CAPE-42 questionnaire at age 19. The high PLEs group at age 19 years exhibited an enhanced response in right insular cortex and decreased response in right prefrontal, right parahippocampal and left striatal regions; also, a gradient of decreasing response to emotional faces with age, from 14 to 19 years, in the right parahippocampal region and left insular cortical area. The right insula demonstrated an increasing response to emotional faces with increasing age in the low PLEs group, and a decreasing response over time in the high PLEs group. The change in parahippocampal/amygdala and insula responses during the perception of emotional faces in adolescents with high PLEs between the ages of 14 and 19 suggests a potential 'aberrant' neurodevelopmental trajectory for critical limbic areas. Our findings emphasize the role of the frontal and limbic areas in the aetiology of psychotic symptoms, in subjects without the illness phenotype and the confounds introduced by antipsychotic medication

Examination of the neural basis of psychotic-like experiences in adolescence during processing of emotional faces

Contemporary theories propose that dysregulation of emotional perception is involved in the aetiology of psychosis. 298 healthy adolescents were assessed at age 14- and 19-years using fMRI while performing a facial emotion task. Psychotic-like experiences (PLEs) were assessed with the CAPE-42 questionnaire at age 19. The high PLEs group at age 19 years exhibited an enhanced response in right insular cortex and decreased response in right prefrontal, right parahippocampal and left striatal regions; also, a gradient of decreasing response to emotional faces with age, from 14 to 19 years, in the right parahippocampal region and left insular cortical area. The right insula demonstrated an increasing response to emotional faces with increasing age in the low PLEs group, and a decreasing response over time in the high PLEs group. The change in parahippocampal/amygdala and insula responses during the perception of emotional faces in adolescents with high PLEs between the ages of 14 and 19 suggests a potential 'aberrant' neurodevelopmental trajectory for critical limbic areas. Our findings emphasize the role of the frontal and limbic areas in the aetiology of psychotic symptoms, in subjects without the illness phenotype and the confounds introduced by antipsychotic medication