Analysis of an Innovative Microchannel Condenser Design for Modular Chillers and Unitary Rooftop Air Conditioners

An innovative way of integrating microchannel condensers in modular chillers and rooftop air conditioners is presented in this paper. The geometrical characteristics of the heat exchanger and how it can be incorporated into commercial air conditioners is discussed. Details are given on the performance analysis of the heat exchanger under at typical chiller operating conditions. Effect of multiple factors such as air entrance losses, fan performance and refrigerant/air mal distribution is analyzed. Analysis shows that the new heat exchanger increases the capacity of a typical chiller condenser by 20%. At same capacity the new heat exchanger resulted in around 2K drop in condensing temperature thereby increasing the chiller efficiency by 5.5%

Modeling, Verification and Optimization of Hybrid Ground Source Heat Pump Systems in Energyplus

Hybrid Ground Source Heat Pump system simulation capability was added to EnergyPlus. Program was modified to handle multi-year simulation capability. New supervisory controls were added and a plate heat exchanger model developed to configure realistic systems. The models were verified by comparing to the published results in literature by Yavuzturk et al. (2000). GenOpt was used to investigate the optimal design, control strategies and configuration. Life cycle cost of the system was used as objective function. Effects of using first year operating cost and 20th year operating cost on optimization results were studied. The modifications and addition of new models successfully modeled HGSHP systems in EnergyPlus. The results obtained from EnergyPlus model agreed well within the modeling differences with Yavuzturk results. Optimization proceeded to decrease the GLHE length to the minimum possible, since it was the highest contributor towards cost. Optimization of HGSHP systems was found to be system specific and highly affected by the load imbalance. Use of 20th year operating cost instead of first year operating cost to calculate the life cycle cost affected the results of optimization.Mechanical & Aerospace Engineerin

Study of Frost Growth on Heat Exchangers Used as Outdoor Coils in Air Source Heat Pump Systems

During winter heating operation, the outdoor coil of a heat pump acts as an evaporator and when the ambient temperature is near freezing, the moisture in the atmospheric air freezes on the coil surface. The frost growth affects the air flow and also adds resistance to heat transfer thus reducing the capacity and the efficiency of the heat pump. An experimental facility is designed and built to test a small scale heat exchanger working in frosting conditions. Tests are carried out using small scale fin-tube and microchannel heat exchanger over a range of glycol inlet temperatures, air velocities and ambient air RH. A semi-empirical frost model based on a scaling approach is developed and applied to both fin-tube heat and microchannel heat exchangers. The model is developed to handle non-uniformities in both refrigerant and air side. The frost model is integrated with a segment-by-segment heat exchanger calculation algorithm and is validated against experimental data. Frost growth model is also incorporated in a quasi-steady state system simulation algorithm.Findings and Conclusions: From the experimental study it was observed that the temperature of the surface and air RH affected the rate of frost growth significantly while the air velocity did not have a great influence. It is demonstrated that a dry heat transfer correlation can be used during frost growth period by correctly accounting for frost thickness in the hydraulic diameter calculations. Ignoring the phenomenon of air redistribution was found to result in errors in the range of 20% to 50% in predicted frost thickness. Frost thickness predicted by the frost model is within 5% of the measured values for most of the cases. Frost mass accumulation predicted by the simple model is higher than the measured values due to a uniform thickness assumption in the model. An improved frost model based on 1-D finite volume discretization is also presented which improved the frost mass prediction to within 13% of measured values. The system simulation is validated against experimental results and found to match reasonable well. The discrepancy between simulation and experiments were due to the effects of system transience in the initial stages.Mechanical & Aerospace Engineerin

Frosting Performance of Fin-and-Tube Evaporators with Small Copper Tubes Diameter

In modern heat pump systems, the heat exchangers use enhanced heat transfer surfaces for both air and refrigerant sides. In air conditioning applications, conventional 9.5 mm (3/8 inch) tube diameter fin-and-tube coils are slowly being replaced by microchannel heat exchangers. However, during heating mode the energy performance of heat pump systems with microchannel outdoor coils are generally lower than those of fin-and-tube direct-expansion evaporators due to a higher frequency of defrost cycles. A different approach might be to utilize fin-and-tube technology, which has proven records of excellent water drainage characteristics and good performance in frosting operating conditions, and enhance the air side heat transfer rates by introducing a larger number of small diameter copper tubes. In this paper, six fin-and-tube coils with copper tube diameter ranging from 5 mm (1/5 inch) to 7mm (8/29 inch) were experimentally investigated in frosting operating conditions. The laboratory experiments were conducted in an air flow wind tunnel at Oklahoma State University. Experimental data on heat transfer rate and air-side pressure drop across the coils were measured and the fin density and the tube diameter were varied in a parametric fashion during the experimental campaign. The performance of the fin-and-tube coils were also compared to those of a conventional 9.5 mm copper tube diameter fin-and-tube heat exchanger and of a microchannel heat exchanger that had similar air-side frontal area and at similar operating conditions of outdoor direct-expansion evaporators in heat pump systems for residential applications. The trends of the data during frosting operation suggested that reducing the tube diameter was beneficial for frosting performance at low fin density while was harmful at high fin density. The data showed that increasing the fin density increased the capacity but significantly reduced the time for heating service for the evaporator. Small copper tube diameter resulted in about 11% higher initial capacity at dry start conditions and about 4% higher average integrated capacity when considering the entire frost period. The data discussed in this paper serve as basis for future research on direct-expansion evaporators for air-source heat pump applications, in which the frosting of the outdoor heat exchangers is still one of the major concerns

FastCLIPstyler: Optimisation-free Text-based Image Style Transfer Using Style Representations

In recent years, language-driven artistic style transfer has emerged as a new type of style transfer technique, eliminating the need for a reference style image by using natural language descriptions of the style. The first model to achieve this, called CLIPstyler, has demonstrated impressive stylisation results. However, its lengthy optimisation procedure at runtime for each query limits its suitability for many practical applications. In this work, we present FastCLIPstyler, a generalised text-based image style transfer model capable of stylising images in a single forward pass for arbitrary text inputs. Furthermore, we introduce EdgeCLIPstyler, a lightweight model designed for compatibility with resource-constrained devices. Through quantitative and qualitative comparisons with state-of-the-art approaches, we demonstrate that our models achieve superior stylisation quality based on measurable metrics while offering significantly improved runtime efficiency, particularly on edge devices.Comment: Accepted at the 2024 IEEE/CVF Winter Conference on Applications of Computer Vision (WACV 2024

Genome sequence and description of Pantoea septica strain FF5

Strain FF5 was isolated from the skin flora of a healthy Senegalese 35-year-old woman. This strain was identified as belonging to the species Pantoea septica based on rpoB sequence identity of 99.7 % with Pantoea septica strain LMG 5345(T) and a highest MALDI-TOF-MS score of 2.3 with Pantoea septica. Like P. septica, this FF5 strain is a Gram-negative, aerobic, motile, and rod-shaped bacterium. Currently, 17 genomes have been sequenced within the genus Pantoea but none for Pantoea septica. Herein, we compared the genomic properties of strain FF5 to those of other species within the genus Pantoea. The genome of this strain is 4,548,444 bp in length (1 chromosome, no plasmid) with a G + C content of 59.1 % containing 4125 protein-coding and 68 RNA genes (including 2 rRNA operons). We also performed an extensive phenotypic analysis showing new phenotypic characteristics such as the production of alkaline phosphatase, acid phosphatase and naphthol-AS-BI-phosphohydrolase

A Descriptive Study of Indian General Public’s Psychological responses during COVID-19 Pandemic Lockdown Period in India

Pandemics like COVID-19 poses several challenges which not only include medical but also have a psycho-social impact on the society. It is important to understand how public appraise a pandemic in a large country like India and how do they mentally and behaviorally respond during this threat. A structured questionnaire was used to collect the data and examine the Health Anxiety, Coping and Locus of Control-Internal/External variables using five-point Likert Scale. Responses (n = 231 ) were collected during 24th March to 30th March; this duration is part of nation-wide lockdown period. There was a significant difference between various age groups and their Health Anxiety. (F (8, 222)=2.772. p<.05). Analysis of health related anxiety reveals that respondents are more worried over the health of their loved ones than theirs. With regard to coping mechanism, it was found that, during the Covid-19 outbreak period, respondents displayed high engagement with the social media and connect with their loved ones using technology. Respondents feel responsible towards disease control, prevention, spread and healthy protective behaviour. The study provides preliminary insights into people’s perception on Health Anxiety, Locus of Control and Coping mechanism

Implementation and validation of ground-source heat pump system models in an integrated building and system simulation environment

This invited paper was written largely by Rees, it flows from several years work funded by the US Department of Energy. The models of the geothermal heat pump systems implemented in the major public domain energy simulation program, EnergyPlus are thus accessible to practitioners internationally and are in active use. Fisher was the project leader, the other authors are PhD students