Indoor Unit Research Articles

Comparative Assessment of Indoor Air Quality and Comfort Parameters in Government and Non-Government Hospitals in Southwestern Bangladesh

Indoor air quality (IAQ) is considered crucial in the hospital environment for the health improvement of the patients and the well-being of all the staff and visitors. Despite that, in a lot of hospitals in developing and underdeveloped countries, IAQ is severely impaired by different factors. The lower-income people are mostly dependent on the government-subsidized public hospital, and that necessarily creates a huge number of patients and gatherings and results in impaired IAQ. In this study, nine hospital wards were selected from one public and one private hospital in the southwestern part of Bangladesh to compare the IAQ with respect to the outdoor values. Five IAQ parameters (PM2.5, PM10, VOC, CO2, and HCHO) and three indoor comfort parameters (temperature, relative humidity, and noise) were assessed at three different times of the day (morning, midday, and after noon). The results suggested that PM2.5, PM10, and CO2 were significantly higher in the private hospital units (48.59±12.34µg/m3, 65.27±14.18µg/m3, and 721.13±159.20ppm, respectively) than the public hospital units. In contrast, temperature and relative humidity were found to be slightly lower in the private hospital units (RH: 81.80±1.29%, T: 31.27±1.24°C) than in the public hospital units. The detected noise level was significantly higher in each hospital's indoor units than the outdoor units. The I/O ratio suggests most contamination sources are indoors for the private hospital units, while the toxicity potential found considerable health implications for those indoor locations.

Cooperative control strategy of variable evaporation temperature and variable superheat degree for a VRF system to improve temperature stability in multiple rooms

The energy consumption of variable refrigerant flow (VRF) systems can be reduced by adopting the variable evaporation temperature and constant superheat degree (VECS) control strategy instead of constant evaporation temperature and constant superheat degree (CECS) control strategy. However, the constant superheat degree control strategy may weaken the adjustment ability of cooling capacity of indoor units, and result in obvious room temperature fluctuations. In order to decrease room temperature fluctuations and reduce energy consumption simultaneously, a cooperative control strategy of variable evaporation temperature and variable superheat degree (VEVS) is proposed, i.e. one indoor unit is chosen to be controlled by variable evaporation temperature and the rest of the indoor units are controlled by variable superheat degrees. In this control strategy, the target value of evaporation temperature is the lowest value among the upper limits of the evaporation temperatures of all indoor units, and the target values of the superheat degrees of indoor units are predicted according to the cooling demands of rooms. Comparative experiments on room temperature fluctuation and energy consumption among the control strategies of CECS, VECS and VEVS are done. It is shown that both the control strategies of VECS and VEVS achieve smaller room temperature fluctuation and lower energy consumption than those of CECS; compared with the VECS control strategy, the average room temperature fluctuation of the VEVS control strategy is decreased from 1.1°C to 0.5°C due to variable superheat degree, and the energy consumption of the VEVS control strategy is reduced by 4.4%.

Tribological analysis of rotor system startup considering deformations of high elastic rubber bushings and grease lubricated plastic bearings

To achieve a compact design, reduced noise, and extended operational lifespan of the air conditioner indoor unit, a novel motor rotor system was implemented. This system utilizes three engineering plastic bearings, encased in high-elasticity rubber bushings and lubricated with grease. Yet, the absence of a simulation model that accurately represents the structural and material properties of this bearing-rotor assembly hampers the precise evaluation of how design parameters influence system performance. As such, in the present study, an innovative tribo-dynamics model was established using a coupling approach that integrates dynamics and tribology. This model encompasses a 4-degree-of-freedom rotor dynamics framework and a grease elastohydrodynamic model, which accounts for the deformation of both rubber bushings and plastic bearings. Utilizing this tribo-dynamics model, the effects of the elastic modulus of the bushing on the tribological properties of the system were explored. The results show that a small elastic modulus of the bushing effectively reduced the local high contact pressure between the journal and the bearing during startup. However, the elastic modulus cannot be excessively low, as it would adversely affect the range of journal motion and the film thickness under rated operating conditions.

Analysis and prediction of energy consumption in office buildings with variable refrigerant flow systems: A case study

Accurately predicting building air-conditioning energy consumption is particularly important for energy management. However, for small datasets, there is a lack of simple and effective prediction methods applicable to multiple buildings. In order to fully explore the energy consumption mode of Variable Refrigerant Flow (VRF) air conditioning system and improve the accuracy of the model. This study uses the weather data of an outdoor meteorological data collection system and the air conditioning system and energy consumption data of an office building in Jinan. Initial analysis revealed that occupant behavior and daily variations in outdoor air temperatures significantly impact the energy consumption of air conditioning systems. Then, by applying the random forest algorithm and Pearson correlation analysis, the study identified daily average outdoor air temperature and VRF indoor unit running time as critical features for prediction. Subsequently, three machine learning models—Multiple Linear Regression (MLR), Back Propagation Neural Network (BPNN), and Long Short-Term Memory (LSTM) neural network—were developed and assessed using a 4:1 training-to-testing set ratio. Comparative analysis revealed that all models performed robustly, with the MLR model exhibited superior predictive accuracy (R2 (Coefficient of Determination) = 0.98, MAE (Mean Absolute Error) = 0.005 kWh/(m2·day), and RMSE (Root Mean Square Error) = 0.007 kWh/(m2·day) for the testing set) and simplicity. Furthermore, the effectiveness of the MLR model in handling small sample sizes was confirmed through cross-validation of data from two additional office buildings, highlighting its suitability for predicting energy consumption of VRF air conditioning systems in office buildings.

Development and validation of intelligent load control for VRF air-conditioning system with deep learning based load forecasting

Variable refrigerant flow (VRF) air-conditioning systems have seen significant growth in Asia and its application is expanding globally. Despite the expanded application, most previous studies have focused on developing fault detection and diagnostics to achieve energy-efficient operations than on predicting power consumption. It's very difficult to predict the electrical consumption owing to its complex system configuration and various control strategies. A new control strategy is described for optimal adjustment of the desired target level based on time series forecasting using the optimized sequence to sequence model for VRF systems. Sequence to sequence (seq2seq) model with attention mechanism and Bayesian optimization is developed to predict accurate hourly and daily forecasts and rapid feedback control for fluctuating power consumption for VRF systems. The optimized seq2seq model is integrated into the intelligent load control (ILC). ILC can be used to manage VRF systems by dynamically prioritizing indoor units for curtailment using both quantitative inputs and qualitative rules. Overall, the results demonstrate that the deep learning based control allows coordination of the controllable loads of VRF systems in three commercial buildings. ILC with deep learning manages the power consumption within a desired target level, as well as indoor temperature reflecting the status of controlled indoor units, as objective functions of the control algorithm.

Energy consumption analysis and operating characteristics research on small time scale of variable refrigerant flow air conditioning systems in public buildings

In order to analyze the energy consumption and operation characteristics of the variable refrigerant flow (VRF) air-conditioning system on small time scale and put forward effective energy-saving suggestions, the VRF system operation experiments are carried out under different indoor set temperatures, different indoor unit opening quantities and different indoor set air velocities. This experiment studies the main influencing factors of energy consumption and operation of the VRF system, such as indoor temperature difference, indoor air velocity, outdoor environment temperature and so on. The results show that the rated power of indoor unit is linearly related to the energy consumption of the VRF system. The total active power changes greatly when the VRF starts and stops, and the outdoor ambient temperature changes. The indoor set air velocities have a great influence on the energy consumption and operation of the VRF system. The performance parameters increase first and then decrease with the increase of compressor frequency and load rate. When the load rate is 40 %∼60 %, the performance parameters can reach 3.2 ∼ 4.2.

Effect of Discharge Cooling using Condensate Water on the Performance of an Air Conditioner: A Field Testing

The effect of discharge cooling using condensate water from the evaporator on the performance of an air conditioner has been experimentally investigated. Instead of laboratory testing, the air conditioner was tested under real conditions, as is generally an AC unit installed in a room. The indoor unit was installed inside the room at a height of 2.6 m from the floor, while the outdoor unit was installed outside at floor level. In this research, the air conditioner was tested under two conditions, i.e., normal condition without discharge cooling and modified condition in which the condensate from the evaporator was flown and dripped to the discharge pipe. The use of discharge cooling could decrease suction and discharge pressure, as well as suction and discharge temperature. It also slightly decreases supply air temperature. Better performance of the air conditioner with the use of discharge cooling was shown by the decrease of power consumption by 3.5% and increase of cooling capacity by 2.45%. As a result, the coefficient of performance (COP) increases by 6.31%.

Experimental study on the impact of indoor unit airflow velocity on the performance of an automotive heat pump system with a suction line heat exchanger

This study aimed to investigate the effect of changing the indoor unit air flow rate on the performance of an automobile heat pump with a suction line heat exchanger. Using a four-way valve, the automotive heat pump system was developed by reversing the refrigerant direction in the automobile air conditioning system, excluding the compressor. A suction line heat exchanger was added to the test system to enhance heat transfer between the liquid and suction lines of the automotive heat pump system. Performance comparisons were first performed for R134a and R1234yf by disabling the suction line heat exchanger. Then, the suction line heat exchanger was activated for R1234yf, and the tests were repeated. Performance comparisons were made for two different compressor speeds and three different indoor unit airflow speeds. It was found that using the heat exchanger in R1234yf operations improved the heating capacity, compressor discharge temperature and coefficient of performance by approximately 1.8 %, 5.1 % and 5.9 %, respectively. The heating capacity of the heat pump system using R134a, R1234yf, and R1234yf with the suction line heat exchanger was determined to be in the range of 2.46–3.29 kW, 2.35–3.04 kW, and 2.39–3.11 kW, respectively. An increase in the airflow speed of the indoor unit from 1.4 m s−1 to 3.2 m s−1 resulted in an average decrease of approximately 12.3 % in the compressor discharge temperature. In contrast, the heating capacity and coefficient of performance increased by approximately 11.8 % and 14.4 % on average, respectively, for R1234yf operations with the heat exchanger. This study revealed that by optimizing the air flow rate in the R1234yf heat pump system with a suction line heat exchanger, improvements in the heating capacity and coefficient of performance can be achieved, thus providing better thermal comfort in the passenger compartment.

Acoustic comfort improvement of simultaneous heating and cooling heat pumps using control logic for flow-induced noise reduction

Acoustic comfort in buildings can be achieved by minimizing unwanted noise generated primarily from heating, ventilation, and air-conditioning systems. However, research on noise reduction in simultaneous heating and cooling heat pumps (SHCHP) is limited. This study proposes a novel noise reduction control logic (NRCL) based on experiments on flow-induced noise through electronic expansion valves (EEVs) in an SHCHP. The flow-induced noise through EEVs was measured and analyzed regarding the degree of subcooling, differential pressure between indoor unit and evaporation (ΔPindoor), EEV opening speed (Vo), and opening (Oeev) while switching operation mode in an SHCHP. For all the operating and controllable variables, the peak sound pressure level (SPLpeak) was decreased by evenly distributing sound energy (SE). The sensitivity analysis indicated that Oeev and Vo were the most significant variables for achieving uniformly distributed SE. Therefore, a novel NRCL was proposed in terms of the initial EEV opening (Oeev,i) and dimensionless control time (CT) derived from the relationship between Oeev and Vo. The optimal CT for EEVs in SHCHP with NRCL was 1. At this point, the difference between SPLpeak and average SPL decreased by 46.2%, and the converging time for ΔPindoor to 0 increased by 17.8% compared with those of baseline.

An Investigation of the Acoustic Enclosure of an Air Conditioning Compressor Using Response Surface Analysis and Topological Rigidity Optimization

A novel split-type air conditioning system is introduced to balance usability and portability. Unlike conventional split-type systems, where the compressor is typically placed outside, this system situates the compressor within the indoor unit, which may expose users to compressor noise. There are prominent peaks in the compressor noise spectrum, particularly at the compressor operating frequency and its harmonics, notably the second and third harmonics. The research presents a multilayered acoustic enclosure specifically designed for air conditioning compressors to address this issue without modifying the compressor or indoor unit casing. In order to get better sound insulation performance, a response surface methodology (RSM) is applied to optimize the thickness ratio, open area ratio, and open area height of the acoustic enclosure with predefined thickness. In addition, topological optimization is employed to strengthen weak areas of the acoustic enclosure. Then, experimental trials using the proposed acoustic enclosure are conducted in a semianechoic chamber. Results demonstrate significant reductions in noise levels, including 7.99 dB(A), 5.69 dB(A), and 5.19 dB(A) reductions in the fundamental frequency, second harmonic, and third harmonic noise of the compressor’s operating frequency, respectively.

Virtual design on the heat pump refrigeration cycle: challenges and approaches

Virtual product design (VPD) of the refrigeration cycle has long been a major subject of many engineers and manufacturers. Issues should be the question of how simulation gets close to the real world in virtual ways. It is especially true when we consider variable refrigerant flow (VRF) heat pumps, having various types of indoor unit combinations, long and complicated piping configurations, and simultaneous cooling and heating functions under extreme weather conditions. In this regard, model-based systems engineering (MBSE) or model-based design (MBD) guides a methodology to make a virtual model easily. Now, there are plenty of engineering platforms and tools to make a strong simulation model, which provides interfacing technology among multiple physics, different dimensions, and codes in different languages. In the study, the authors share their experience in the virtual design for a VRF heat pump system including the architecture, multiple physics, and the connection with the control SW. Modelica, an acausal and object-oriented modeling language, constructs the backbone of the model to describe the dynamic behavior of refrigerants and to combine external components in the form of functional mock-up units (FMUs). The developed virtual model is validated against measured data, showing it can reproduce all the essential physics of interest both in qualitative and quantitative ways.

Indoor space risk assessment based on Co-analysis strategy in split room air conditioning

The use of environmentally friendly hydrocarbon refrigerants in air conditioning systems is being promoted worldwide as a proactive measure to combat global warming and ozone depletion. A comprehensive analysis of hydrocarbon refrigerant leakage and the resulting fire risk is essential for split room air conditioning (SRAC) systems. The study presents a novel Co-analysis strategy that integrates the operation of SRAC systems with the assessment of indoor space fire risk. Experiments involving the leakage and diffusion of R-290 in SRAC system have been conducted to substantiate the validity of the Co-analysis strategy. This model is used to analyze the dynamic parameters of leakage and distribution patterns of hazardous areas within the SRAC indoor unit. The study considers various leakage hole sizes (1 mm, 2 mm, 3 mm) under both cooling and heating operating modes. The results show the leaking refrigerant flow rate presents different attenuation types under cooling and heating modes. When the leakage hole diameter is less than 2 mm in the cooling mode, the concentration of R-290 in the space is below 50 % lower flammable limit. The comprehensive fire risk probability of the R-290 indoor unit is 1.0 × 10−11∼5.0 × 10−10 for the cooling model and 1.0 × 10−11∼9.0 × 10−10 for the heating model. Effective methodologies for mitigating risks and optimizing the system are also proposed. Based on the Co-analysis strategy, this study presents a scientifically grounded assessment of the fire risk associated with air conditioning uses flammable refrigerants inside buildings. The strategy aims to enhance building safety.

Wall-embedded micro heat pump for radiant heating in buildings: Evaluation of energy and thermal comfort performance

This paper presents a novel radiant heating system with a wall-embedded micro heat pump (WEMHP) for residential buildings. The interior surface temperature of the exterior wall-section empowered by the micro heat pump is independently controlled, enabling distributed thermal comfort delivery. The micro heat pump consists of a miniature compressor along with an aluminum roll-bond condenser and evaporator. In contrast to conventional hydronic radiant systems and heat pumps with separate indoor and outdoor units (i.e., split systems), the WEMHP is a “packaged” system that would not require on-site installation and charging of a secondary water loop and circulation pump or refrigerant piping. This could ultimately lead to reduced installation and maintenance costs. In this study, a detailed system model is presented and integrated with a single-zone building model to assess the energy performance of the WEMHP in heating mode. For a designed living room scenario with an external wall WEMHP-to-wall ratio (HPWR) of 0.6 and window-to-wall ratio (WWR) of 0.2, the simulation results show that up to 23 % energy savings compared with a baseline air-to-air heat pump are possible. The results also indicate the HPWR needs to be higher than 0.4 to achieve performance comparable to the baseline. Additionally, experiments were conducted in a laboratory environment in which surface temperatures were controlled to emulate different scenarios for integration of WEMHP technology and to evaluate thermal comfort conditions. The experimental results show that the median operative temperature differences in the indoor environment were within 0.5 °C for various locations while the largest radiant asymmetry was 2.2 °C for the designed room configuration. Moreover, simulations were conducted to evaluate thermal comfort conditions in applications having a smaller HPWR of 0.4 with various values of WWR. Overall, the combined simulation and experimental study shows that the WEMHP has potential to reduce energy use while maintaining thermal comfort at acceptable levels where the HPWR is higher than 0.4.

Modeling and experimental investigation of oil retention in pipelines of multi-split air conditioning system

A multi-split air conditioning system may suffer damage caused by oil starvation in its compressor when the lubricating oil largely retains in long pipelines, and thus a reasonable oil charge based on accurate prediction of the oil retention in pipelines is important. The purpose of this study is to present an oil retention model for pipelines and to experimentally validate this model. The structure of pipelines connecting the outdoor unit and the indoor units with arbitrary numbers installed on separated floors is described as a combination of straight pipe types, joint types, and bend types. In modeling the oil retention, all the components of straight pipes, joints, and bends are numbered to conveniently distinguish each component which is further divided into several control volumes with equal lengths along the flow direction, and the equations of oil retention, pressure drop and enthalpy difference for the control volumes are established to describe the refrigerant-oil flow behavior. A hierarchical iterative algorithm based on the graph theory is developed in order to solve the models quickly. An experimental rig is built to measure the oil retention in four types of straight pipes, and the validation results show that the predicted oil retention in straight pipes agrees with at least 74.0 % of the experimental data within a deviation of ±20 %, and the mean deviation is lower than 15.4 %. Based on the model, the effects of oil retention reduction by increasing the total mass flow rate or the evaporation temperature of refrigerant are quantitatively analyzed.

Optimal refrigerant flow configurations in a fin-tube heat exchanger for an indoor unit of a heat pump using R466A

Optimal refrigerant flow configurations in a fin-tube heat exchanger for an indoor unit of a heat pump using R466A

Unilateral Lung Parenchymal Infiltrates with GGO & Evolving Consolidation as Presenting Feature of Sporadic COVID-19 Pneumonia in Post Pandemic Era in a Patient with Acute Febrile Respiratory Illness

Sporadic COVID-19 cases will be predicted to occur in coming few years ahead as observed in previously known influenza virus related pandemics. Herd immunity due to natural infection and hybrid immunity after COVID-19 vaccination has played crucial role in waning of this pandemic. COVID-19 pneumonia has a very ‘typical’ radiological presentations, observed globally; classified as GGO and consolidations involving peripheral parts of lung, bilateral disease, predominantly pleural based areas initially and involves central portions as disease process advances. Such radiological presentations are never documented in history before this pandemic, which has helped in suspecting COVID-19 illness in cases with negative microbiological results initially and such illness were classified as SARI (severe acute respiratory illness). Cases with typical radiological features for COVID-19 with RT PCR positive results were defined as case of COVID-19 illness. Both the clinical scenarios were managed with similar protocol during hospitalization. COVID-19 case burden has significantly decreased in last one year since declaration of end of pandemic by WHO and now we are in post pandemic phase. Since beginnings of pandemic, many corona virus variants were emerged with variable infectivity, virulence, pathogenesis, mortality and morbidity. As pandemic is over, cases are rarely observed with lung involvement, COVID RT PCR testing, HRCT reporting’s in line with pandemic protocol and requirement of resources to treat these cases are less required and utilized today. In present case report, 32-year male, presented in outdoor unit with history of acute febrile respiratory illness with dry cough, high grade fever and chest tightness and chest discomfort of acute onset. HRCT thorax documented Pleural based, peripheral, unifocal or solitary opacity with predominant GGOs in right lower lobe with normal left lung. He is treated in indoor unit in line with community acquired pneumonia protocol and observed clinical worsening with four-fold raised in inflammatory markers. Oxygenation is worsened and raised IL-6, CRP and LDH has given clue to think towards COVID-19 etiology. Thorat swab for COVID-19 RT PCR is positive and managed according to protocol for COVID-19 illness. This is the only observed COVID-19 pneumonia case in last six months, in which; clinical-radiological patters were typical of pandemic illness of second wave of COVID-19 illness due to delta variant. Our case is the sporadic case reported with all clinical features of pandemic illness. We have suspected COVID-19 etiology in spite of ‘atypical unilateral lung involvement’ due to worsened clinical features and abnormally raised inflammatory markers with poor response to standard treatment protocol for community acquired pneumonia. High index of suspicion is must, and; timely interventions with use of rational treatment including remdesivir, heparin & steroids combination during hospitalization has documented successful outcome. We recommend COVID-19 RT PCR testing in all community acquired cases nonresponding to standard guidelines to have timely diagnosis and treatment. Sporadic cases rare to occur, and they do occur for few years ahead of this end of pandemic due to virus variant, and we must quote ‘rare things are not rare to happen’.

Variable evaporating temperature control strategy for a VRF system based on continual estimation of cooling capacity demand of rooms

A variable refrigerant flow system has multiple indoor units for cooling different rooms, and the cooling capacity supply of indoor units depends on evaporating temperature. Existing control strategies of VRF systems generally adopt a constant evaporating temperature which should be low enough to meet the large cooling capacity demand under full load condition, resulting in low energy efficiency. In order to improve energy efficiency, a variable evaporating temperature control strategy is developed, in which evaporating temperature is permitted to rise with the decrease of cooling capacity demand under part load conditions. During the control process, cooling capacity demand of rooms is continually estimated based on indoor thermal balance and room temperature response, and the target evaporating temperature is predicted based on the balance between the cooling capacity supply of indoor units and the cooling capacity demand of rooms. The proposed control strategy has been applied in a VRF system, and its energy efficiency and room temperature variation are tested and compared with those of a same type VRF system that adopts the constant evaporating temperature control strategy. It is shown that the proposed control strategy can improve energy efficiency by 12.6 % and control room temperature fluctuations within ± 0.5 °C.

Role of IL-6 as ‘core inflammatory marker’ in assessment of severity, response to therapy and predicting outcome in COVID-19 pneumonia: A single center experience of 2400 cases in tertiary care setting in India

Objectives: In coronavirus disease-19 (COVID-19) pneumonia, the role of various inflammatory markers including interleukin-6 (IL-6) was evolved in managing cases in indoor or critical care units worldwide. Apart from the role of IL-6 in predicting cytokine storms, the role in assessing post-COVID outcome is less studied. In the present study, we have analyzed the role in predicting ventilatory support requirement and final outcome in COVID-19 pneumonia. Material and Methods: A prospective, observational, and 12 weeks follow-up study included 2400 COVID-19 cases confirmed with reverse transcription-polymerase chain reaction. All cases were assessed with lung involvement documented and categorized on high-resolution computerized tomography (HRCT) thorax, oxygen saturation (SpO2), and IL-6 at entry point and follow-up. Covariates such as age, gender, and comorbidity; interventions such as oxygen use, bi-level positive airway pressure/non-invasive ventilation (BIPAP/NIV); and timings of ventilatory support and final outcome as with or without lung fibrosis as per computed tomography severity were recorded. Covariates were analyzed with initial and sequential IL-6 titer. Statistical analysis is done by Chi-square test. Results: The study of 2400 COVID-19 pneumonia cases, age (<50 and >50 years), gender, and comorbidity has a significant association with IL-6 titer (P < 0.00001). HRCT severity score at entry point and duration of illness has a significant correlation with IL-6 level (P < 0.00001). IL-6 titer has a significant association with SpO2 and BIPAP/NIV requirement during hospitalization (P < 0.00001). Timing of BIPAP/NIV requirement during the course of hospitalization in the intensive care unit has a significant association with IL-6 titer (P < 0.00001). Follow-up IL-6 titer during hospitalization as compared to entry point normal and abnormal IL-6 has a significant association in post-COVID lung fibrosis (P < 0.00001). Follow-up IL-6 titer during hospitalization as compared to entry point abnormal IL-6 has a significant association in predicting cytokine storms irrespective of normal or abnormal IL-6 at entry point (P < 0.0001). Conclusion: IL-6 titer has documented a very important role in triaging the COVID-19 pneumonia cases in indoor units, and guided treatments have shown improved outcomes. IL-6 titer is the “game changer” inflammatory marker not only in assessing the severity or predicting course during hospitalization but it has also helped in the utilizations of timely interventions required during hospitalizations. Sequential IL-6 titer has shown a significant role in predicting final radiological outcomes at 12 weeks.

CT severity Radiological phenotypes (CTS) assessment in COVID-19 pneumonia as ‘inconsistent predictor of disease severity’: A large tertiary care center study in India

Introduction: Radiological phenotypes are radiological patterns or observable characteristics of COVID-19 pneumonia. Various phenotypic classifications have been reported in literature. CT severity radiological phenotypes are widely used and universally accepted radiological phenotypic methods. Robust data is available regarding role of HRCT in COVID-19 pneumonia and we have evaluated role of CT severity in assessing natural course of COVID-19 illness during its evolution sand follow-up. Methods: Prospective, Observational study, included 3000 COVID-19 RT-PCR confirmed cases with lung involvement documented and radiological severity phenotypes categorized on HRCT thorax as mild, moderate and severe as per lung segment involvement bilaterally (scoring tool 0-25 score, mild 1-7, moderate 8-15 and severe 16-25). Radiological CT severity phenotypes were evaluated in correlation with interventions such as oxygen support and oxygen plus ventilatory support requirement during hospitalization. Age, gender, Comorbidity, laboratory parameters and use of BIPAP/NIV in COVID-19 cases and outcome as with or without lung fibrosis were key observations. Final radiological outcome documented in follow up CT thorax imaging done at six months of discharge from hospital. Statistical analysis is done by using Chi square test. Results: In study of 3000 cases, ‘mild, moderate and severe’ radiological CT severity phenotypes were documented as 13.33%, 48.33% & 38.34 % respectively. CT severity has documented significant association with duration of illness at entry point [p<0.00001] Duration of illness (<7 days, 7-14 days and >14 days) plays a crucial role in predicting radiological CT severity phenotypes. CT severity has documented significant association with laboratory parameters at entry point (d-dimer, CRP, IL-6) [p<0.00001] and interventions required in indoor unit. [p<0.00001] Post COVID-19 lung fibrosis or sequelae has significant association with radiological CT severity phenotypes. [p<0.00001] Covariates such as age, gender, diabetes mellitus, IHD, Hypertension, COPD, Obesity has significant association with radiological CT severity phenotypes. [p<0.00001] Conclusion: Radiological CT severity phenotypic differentiation has documented very crucial role in initial assessment and during triaging of these cases in indoor and outdoor setting. Although CT severity is best predictor of severity it has showed ‘inconstancy’ in predicting disease severity, targeting interventions and predicting early and long-term outcomes in COVID-19 pneumonia. J MEDICINE 2024; 25: 46-57

A matter of design and coupling: high indoor charging efficiencies with organic solar modules directly coupled to a sodium ion battery

Generalized framework for the design of indoor power units for autonomous Internet of Things (IOT) devices results in record efficiency combination of organic PV and sodium ion battery.