Solar-Driven Air-Conditioning Cycles: A Review

Most conventional cooling/refrigeration systems are driven by fossil fuel combustion, and therefore give rise to emission of environmentally damaging pollutants. In addition, many cooling systems employ refrigerants, which are also harmful to the environment in terms of their Global Warming Potential (GWP) and Ozone Depletion Potential (ODP). Development of a passive or hybrid solar-driven air-conditioning system is therefore of interest as exploitation of such systems would reduce the demand for grid electricity particularly at times of peak load. This paper presents a review of various cooling cycles and summarises work carried out on solar-driven air-conditioning systems

Investigation on the performance of air source heat pump system with new environment friendly refrigerants for a low carbon building

Energy is an important development factor. It is consumed in different format from different sources in daily human activities. Solar energy, as the most fundamental renewable energy resource, serves in a clean, domestic and environmentally friendly way with minimum impact on surroundings. Due to the ability of transferring heat from low temperature to high temperature, heat pump systems can make great use of natural resources and waste heat resources for the purpose of space heating. Based upon this theoretical principle, this paper presents an investigation on the performance of air source heat pump (ASHP) system with new environment friendly refrigerants, such as R1233zd(E), R1234YF, R1234ze(Z) and R1234ze(E). At the same time, some conventional refrigerants (R134a, R245fa and R123) have been investigated as well for results comparison. A MATLAB program has been developed with the assistance of the database of CoolProp. The results show that the use of some selected environment friendly refrigerants in air source heat pump system for building application alongside other refrigeration applications in strongly recommended

Theoretical investigation of soil-based thermal energy storage system for greenhouses

In this short communication, a novel thermal energy storage system for greenhouses is presented. The novel system is based on directly heating a particular mass of soil through the solar power and utilizing the energy stored in critical months such as November, December, January and February. The target mass of soil is placed beneath the greenhouse with a height of 2m and the boundaries are well-insulated via vacuum insulation panels to provide adiabatic conditions yielding to no heat loss from the edges. Through electric heaters placed inside the target mass of soil, thermal energy is stored inside the soil via the power coming from photovoltaic (PV) panels fixed on the roof of the greenhouse. A specific thin film PV glazing technology called heat insulation solar glass (HISG) is preferred for the power input to the greenhouse. As the first aim of the research, heating demand of the greenhouse is determined for each month. Temperature difference and overall heat transfer coefficient between indoor and outdoor environment are considered to be independent variables in the analyses. Secondly, soil-based thermal energy storage system is introduced and its potential contribution to the heating demand is discussed. The preliminary results indicate that the soil mass is a dominant parameter in soil temperature and hence the thermal energy storage capacity. For a soil mass of 250 tonne, around 600K soil temperature is achieved by the end of year, which is very remarkable

Experimental Investigation of an Indirect Evaporative Cooler Consisting of a Heat Pipe Embedded in Porous Ceramic

An indirect evaporative cooler incorporating a porous ceramic and a heat pipe was described. Experiments were carried out to examine the effects of various ceramic properties, such as porosity, wall thickness, and outside diameter. Use of the cooler for a chilled ceiling in an environmental chamber was also investigated.Atemperature drop of 3.8oC per square metre of ceramic surface area was achieved for an 18 m chamber

Testing and performance analysis of a hollow fiber-based core for evaporative cooling and liquid desiccant dehumidification

In this study, an innovative heat and mass transfer core is proposed to provide thermal comfort and humidity control using a hollow fiber contactor with multiple bundles of micro-porous hollow fibers. The hollow fiber-based core utilizes 12 bundles aligned vertically, each with 1,000 packed polypropylene hollow fibers. The proposed core was developed and tested under various operating and ambient conditions as a cooling core for a compact evaporative cooling unit and a dehumidification core for a liquid desiccant dehumidification unit. As a cooling core, the fiber-based evaporative cooler provides a maximum cooling capacity of 502 W with a wet bulb effectiveness of 85%. As a dehumidification core and employing potassium formate as a liquid desiccant, the dehumidifier is capable of reducing the air relative humidity by 17% with an overall dehumidification capacity of 733 W and humidity effectiveness of 47%. Being cheap and simple to design with their attractive heat and mass transfer characteristics and the corresponding large surface area-to-volume ratio, hollow fiber membrane contactors provide a promising alternative for cooling and dehumidification applications

Smell-related quality of life changes after total laryngectomy : a multi-centre study

Purpose: A total laryngectomy creates an alternate airway for gas exchange that bypasses the upper aerodigestive tract. The subsequent reduction in nasal airflow, and therefore, reduction in deposition of particles to the olfactory neuroepithelium leads to hyposmia or anosmia. The aim of this study was to assess the quality of life impairment conferred by anosmia following laryngectomy and identify any specific patient-related risk factors that are associated with poorer outcomes. Methods: Consecutive patients with a total laryngectomy presenting for review at three tertiary head and neck services (in Australia, the United Kingdom and India) over a 12-month period were recruited. Patient demographic and clinical data were collected, and each subject completed the validated assessment of self-reported olfactory functioning and olfaction-related quality of life questionnaire (ASOF). Dichotomous comparisons were performed using the student's unpaired t-test for continuous variables (SRP), a chi-squared test for categorical variables, and a Kendall's tau-b for ordinal variables (SOC) to assess for a correlation with poorer questionnaire scores. Results: A total of 66 laryngectomees (13.4% female; age 65.7 ± 8.6 years) were included in the study. The mean SRP score of the cohort was found to be 15.6 ± 7.4, while the mean ORQ score was noted to be 16.4 ± 8.1. No other specific risk factors associated with poorer quality of life were identified. Conclusion: A significant quality of life detriment from hyposmia is conferred following laryngectomy. Further research to assess treatment options and the patient population that would best benefit from these interventions is required

Development of Paracetamol-Caffeine co-crystals to improve compressional, formulation and in-vivo performance

Paracetamol, a frequently used antipyretic and analgesic drug, has poor compression moldability owing to its low plasticity. In this study, new co-crystals of paracetamol (PCM) with caffeine (as a co-former) were prepared and delineated. Co-crystals exhibited improved compaction and mechanical behavior. A screening study was performed by utilizing a number of methods namely dry grinding, liquid assisted grinding (LAG), solvent evaporation (SE) and anti-solvent addition using various weight ratios of starting materials. LAG and SE were found successful in the screening study. Powders at 1:1 and 2:1 weight ratio of PCM/CAF by LAG and SE respectively resulted in the formation of co-crystals. Samples were characterized by PXRD, DSC and ATR-FTIR techniques. Compressional properties of PCM and developed co-crystals were analyzed by in-die heckle model. Mean yield pressure (Py), an inverse measure of plasticity, obtained from the heckle plots decreased significantly (p<0.05) for co-crystals than pure drug. Intrinsic dissolution profile of co-crystals showed up to 2.84 fold faster dissolution than PCM and physical mixtures in phosphate buffer pH 6.8 at 37 oC. In addition co-crystals formulated into tablets by direct compression method showed better mechanical properties like hardness and tensile strength. In vitro dissolution studies on tablets also showed enhanced dissolution profiles (~90- 97%) in comparison to the tablets of PCM prepared by direct compression (~55%) and wet granulation (~85%) methods. In a single dose sheep model study co-crystals showed up to two fold increase in AUC and Cmax. A significant (p < 0.05) decrease in clearance as compared to pure drug was also recorded. In conclusion new co-crystals of PCM were successfully prepared with improved tabletability in-vitro and in-vivo profile. Enhancement in AUC and Cmax of PCM by co-crystallisation might suggest the dose reduction and avoidance of side effects