BUBBLE-PUMP-DRIVEN SOLAR ABSORPTION AIR CONDITIONING FOR RESIDENTIAL APPLICATIONS

Large-scale heat-driven absorption cooling systems are currently available in the marketplace for industrial applications. The high temperature is required in the generator for driving this absorption chiller. For this reason, this type of chiller was originally designed to use direct-fired gas. However, the low efficiency of this cooling cycle restricts its use in small-scale applications. The concept of a solar-driven absorption chiller can satisfy the increasing demand for air conditioning without contributing greenhouse gases to the global environment. This research contributes to providing an efficient air conditioning driven by low temperature solar heat and independent of grid electricity, which may be useful in remote residential communities. The performance of 10 kW absorption and adsorption cooling systems were compared for the selection of a suitable cooling technology that can be driven by low temperature heat source such as a flat plate solar collector. Analysis revealed that under any operating conditions, the coefficient of performance (COP) of the absorption cooling system is higher. However, absorption chillers have a lower efficiency than traditional compression refrigeration systems, when used for small scale applications. Hence, energy and exergy analyses were conducted to evaluate the performance of a solar-driven air-cooled ammonia-water absorption chiller for residential air conditioning. Low driving temperature heat sources were optimized (70~80℃) and the efficiencies (COP=0.6, exergetic efficiency=32%) of the system were evaluated. The highest exergy losses were identified in the absorption process (63%) followed by the generator (13%) and the condenser (11%). In order to replace the only electrical component (pump) in an absorption chiller and make it independent of grid electricity, a solar-thermal-driven bubble pump was introduced in a vapor absorption refrigeration (VAR) cycle. This solar-thermal-driven pump can circulate the solution to the absorber and the generator to create the necessary refrigerant vapor for cooling. An analytical model of a bubble pump was developed and experimental work was conducted. Furthermore, a dimensional analysis was performed, considering bubble pump geometry and the solution properties. The bubble pump performance was defined in terms of non-dimensional parameters which can be used in all bubble-pump-driven absorption refrigeration systems. Experimental and theoretical results for a new refrigerant-absorbent solution (LiCl-H2O) were compared, and the flow regime (slug flow) was determined for the highest pump efficiency. Moreover, in order to employ the advantages of high performance, the bubble pump was incorporated into a simulation of a water-based vapor absorption refrigeration cycle. A new absorbent-refrigerant pair (LiCl-H2O) for a bubble-pump-operated VARS was proposed and a thermodynamic comparison was made between LiBr-H2O and LiCl-H2O systems. Finally, energy, exergy and advanced exergy analyses were performed on this proposed refrigeration cycle, and the exergy losses due to the internal irreversibilities of each component and the effect of the irreversibilities of the other components were determined. The avoidable exergy destruction was identified pertaining to the potential improvement of the overall system structure. The highest avoidable endogenous exergy losses occurred in the generator

Residential solar air conditioning: Energy and Exergy analyses of an ammonia-water absorption cooling system

Large scale heat-driven absorption cooling systems are available in the marketplace for industrial applications but the concept of a solar driven absorption chiller for air-conditioning applications is relatively new. Absorption chillers have a lower efficiency than compression refrigeration systems, when used for small scale applications and this restrains the absorption cooling system from air conditioning applications in residential buildings. The potential of a solar driven ammonia-water absorption chiller for residential air conditioning application is discussed and analyzed in this paper. A thermodynamic model has been developed based on a 10 kW air cooled ammonia-water absorption chiller driven by solar thermal energy. Both energy and exergy analyses have been conducted to evaluate the performance of this residential scale cooling system. The analyses uncovered that the absorber is where the most exergy loss occurs (63%) followed by the generator (13%) and the condenser (11%). Furthermore, the exergy loss of the condenser and absorber greatly increase with temperature, the generator less so, and the exergy loss in the evaporator is the least sensitive to increasing temperature

Energy efficiency and economic feasibility of an absorption air-conditioning system using wet, dry and hybrid heat rejection methods

In tropical and sub-tropical regions, air-conditioning systems account for the greatest electricity consumption and high water use. Solar-driven absorption cooling systems can conveniently reduce electricity consumption at need. The performance of this cooling system depends on the system’s heat rejection. A simulation was performed for a 15 kW single effect ammonia-water absorption cooling system driven by low temperature thermal energy and with three different heat rejection methods (wet cooling, dry cooling, and hybrid cooling). This hybrid cooling system uses wet cooling on the absorber and dry cooling on the condenser. The system performance and economics of the chiller with these cooling methods were evaluated. The analysis showed that a wet cooling system has a higher system performance and water consumption compared to a dry cooling system, which has a high primary energy consumption with no water usage. In hot weather conditions and where there is scarcity of water, hybrid cooling can consume on average 41% less electrical energy than dry cooling and 49% less water than wet cooling and the payback period compared to a wet cooling system can be less than three years

Bubble-pump-driven LiBr-H2O and LiCl-H2O Absorption Air-Conditioning Systems

A thermally-driven bubble pump, powered by solar or waste heat energy, is a simple and efficient technique for lifting a liquid from lower to higher levels, after which it can flow by gravity. In this study, solar thermal driven pumps were incorporated in the solar collector as well as in the refrigerant cycle to provide a design of an air-conditioning system for a residential home that is independent of grid electricity. The crystallization challenge, low pressure, and low efficiency are the main downsides of bubble-pump-driven LiBr-H2O refrigeration systems, in comparison with other bubble-pump-driven diffusion absorption refrigeration systems. Therefore, a complete thermodynamic analysis of each component is necessary to improve the system performance. In this research, a thermodynamic model was developed, introducing a new absorbent-refrigerant pair (LiCl-H2O) and comparing it with LiBr-H2O, in a bubble pump operated absorption chiller driven by solar thermal energy. Under the same operating condition, the highest cooling effect and the performance of the LiCl-H2O system are 49 W and COP=0.56 compared to 34 W and COP=0.46 for a LiBr-H2O system

Sintesis Silika Gel dari Abu Sekam Padi Termodifikasi Kitosan serta Aplikasinya sebagai Adsorben Methylene blue

ABSTRACT                  Synthesis of silica gel from chitosan-modified rice husk ash and its application as an adsorbent of methylene blue have been studied. The stages of this research included the preparation of rice husk samples, the synthesis of silica ash of rice husks, sodium silicate, chitosan solution, and synthesis of silica gel - chitosan - tripolyphosphate, and the characterization of silica gel material from chitosan-modified rice husk ash. The results showed that silica gel adsoerben from chitosan modified rice husk ash was able to adsorb methylene blue dyes with an optimum pH of 5, optimum contact time for 60 minutes and adsorption capacity of 16.4554 mg/g.   Keywords: rice husk, silica gel, chitosan, methylene blue.ABSTRAK               Sintesis silika gel dari abu sekam padi termodifikasi kitosan serta aplikasinya sebagai adsorben methylene blue telah dilaksanakan. Tahapan penelitian ini adalah preparasi sampel sekam padi, sintesis silika abu sekam padi, pembuatan natrium silikat, pembuatan larutan kitosan, sintesis silika gel – kitosan - tripolifosfat, serta karakterisasi material silika gel dari abu sekam padi termodifikasi kitosan. Hasil penelitian menunjukkan bahwa adsoerben silika gel dari abu sekam padi termodifikasi kitosan mampu mengadsorpsi zat warna methylene blue dengan pH optimum 5, waktu kontak optimum selama 60 menit dan kapasitas adsorpsi sebesar 16,4554 mg/g.   Kata kunci: sekam padi, silika gel, kitosan, methylene blue

Advanced Exergy Analysis Of Licl-H2O Absorption Air Conditioning System

Increasing energy demand for air conditioning due to climate change is posing a continuous threat to the environment. Absorption air-conditioning systems driven by solar thermal or waste heat energy are an alternative for providing cooling comfort in a sustainable manner. The crystallization problem of high performance LiBr-H2O absorption cooling system hinders its small-scale applications. In this study, the potential of a 10 kW LiCl-H2O absorption refrigeration system is discussed and analyzed. The new concept of advanced exergy analysis is coupled with conventional thermodynamic analyses, which provides the available potential of each component for overall system performance improvement. The analyses uncovered that only 45% of the total exergy loss is due to each component’s own internal irreversibilities, whereas the remaining is through the interaction of the irreversibilities of other components in the system. The analyses also reveal that 43% of the total exergy loss is unavoidable and 57% can be reduced by improving the overall system efficiency

Validasi Metode Penentuan Mn Dalam Oli Lubrikan Dengan Metode Pengenceran Langsung Menggunakan Spektrofotometer Serapan Atom

Validation method on the determination of Mn in lubricating oil by direct dilution method using Atomic Absorption Spectrophotometer (AAS) in Laboratory & Environment Control PT. Badak NGL Bontang has been done The validation method was done with research stages such as determination of  optimum solvent, and determination of some important parameters influential for validation method such as parameter of liniearitas (r), Instrument Detection Limit (IDL), Methode Detection Limit (MDL), accuracy, precision, Limit of Detection(LOD) and Limit of Quantitation(LOQ). The result of research obtain is good, showed that the linearity value with R2 ≥ 0,997. The IDL and MDL value was 0.0021 ppm and 0.0092 ppm respectively and has been acceptability requirements of MDL. The accuracy paramater obtained recovery value with range 82.25-88.34%. The measurement of repeatability and reproducibility, the CV Horwitz value smaller than % RSD, indicating the method had a good precision. The measurement of  LOD and LOQ value was 0.095 ppm 0.317 ppm respectively. Based on the result of the research determination method of Mn in lubricating oil by direct dilution method using AAS concluded valid

In vitro anti-angiogenic properties of ethanolic crude extract of Vernonia amygdalina

Angiogenesis is the process of generating new blood vessels that deliver tumor cells with oxygen and essential nutrients for growth and metastasis. This study examined the in vitro antiangiogenic properties of the ethanolic crude extract from Vernonia amygdalina (VA) grown in Malaysia. The direct antiangiogenic activity of VA was evaluated on EA.hy926 cells using in vitro assessments: Cell proliferation, colony formation, migration, and cell invasion assays. VA ethanolic crude extract cytotoxic activity was evident in the antiproliferative and colony formation assays. The growth inhibition (IC50) of 50% against EA.hy926 endothelial cells was achieved after 72 h treatment at a concentration of 85.43±3.57 μg/mL. Upon 48 h treatment, colony formation was inhibited completely at 100 μg/mL while 51.94% inhibition was achieved at 50 μg/mL. Moreover, the extract showed 54.72% and 31.99% inhibitory effects against migration of cells when treated for 24 h treatment at two different concentrations, 25 μg/mL and 12.5 μg/mL, respectively. The use of 100 μg/mL VA ethanolic extract inhibited cell invasion by 35.43%, which was lower than that of 57.81% inhibition achieved by the vinblastine as a positive control. All in all, the present work clearly demonstrated the antiangiogenic properties of VA ethanolic extract that may reflect a chemotherapeutic and/or chemoprevention potential for biomedical applications

Stunting as a Synonym of Social Disadvantage and Poor Parental Education

Socially, economically, politically and emotionally (SEPE) disadvantaged children are shorter than children from affluent background. In view of previous work on the lack of association between nutrition and child growth, we performed a study in urban schoolchildren. We measured 723 children (5.83 to 13.83 years); Kupang, Indonesia; three schools with different social background. We investigated anthropometric data, clinical signs of malnutrition, physical fitness, parental education, and household equipment. Subjective self-confidence was assessed by the MacArthur test. The prevalence of stunting was between 8.5% and 46.8%. Clinical signs of under- or malnutrition were absent even in the most underprivileged children. There was no delay in tooth eruption. Underprivileged children are physically fitter than the wealthy. The correlation between height and state of nutrition (BMI_SDS, skinfold_SDS, MUAC_SDS) ranged between r = 0.69 (p < 0.01) and r = 0.43 (p < 0.01) in private school children, and between r = 0.07 (ns) and r = 0.32 (p < 0.01) in the underprivileged children. Maternal education interacted with height in affluent (r = 0.20, p < 0.01) and in underprivileged children (r = 0.20, p < 0.01). The shortness of SEPE disadvantaged children was not associated with anthropometric and clinical signs of malnutrition, nor with delay in physical development. Stunting is a complex phenomenon and may be considered a synonym of social disadvantage and poor parental education

MesoTRAP: a feasibility study that includes a pilot clinical trial comparing video-assisted thoracoscopic partial pleurectomy decortication with indwelling pleural catheter in patients with trapped lung due to malignant pleural mesothelioma designed to address recruitment and randomisation uncertainties and sample size requirements for a phase III trial.

Introduction: One of the most debilitating symptoms of malignant pleural mesothelioma (MPM) is dyspnoea caused by pleural effusion. MPM can be complicated by the presence of tumour on the visceral pleura preventing the lung from re-expanding, known as trapped lung (TL). There is currently no consensus on the best way to manage TL. One approach is insertion of an indwelling pleural catheter (IPC) under local anaesthesia. Another is video-assisted thoracoscopic partial pleurectomy/decortication (VAT-PD). Performed under general anaesthesia, VAT-PD permits surgical removal of the rind of tumour from the visceral pleura thereby allowing the lung to fully re-expand. Methods and analysis: MesoTRAP is a feasibility study that includes a pilot multicentre, randomised controlled clinical trial comparing VAT-PD with IPC in patients with TL and pleural effusion due to MPM. The primary objective is to measure the SD of visual analogue scale scores for dyspnoea following randomisation and examine the patterns of change over time in each treatment group. Secondary objectives include documenting survival and adverse events, estimating the incidence and prevalence of TL in patients with MPM, examining completion of alternative forms of data capture for economic evaluation and determining the ability to randomise 38 patients in 18 months. Ethics and dissemination: This study was approved by the East of England-Cambridge Central Research Ethics Committee and the Health Research Authority (reference number 16/EE/0370). We aim to publish the outputs of this work in international peer-reviewed journals compliant with an Open Access policy. Trial registration: NCT03412357