Reducing the amount of required propane refrigerant in the condenser of a commercial air-conditioner by increasing the inlet temperature

The use of synthetic refrigerants in the refrigeration and air conditioning sector is now obsolete due to the fact that they are not environmental friendly. They damage ozone layer and cause global warming which have both direct and indirect adverse effects on humans and environment. Today, the use of alternative refrigerants is well accepted. Hydrocarbon refrigerants are natural compounds, which do not damage the ozone layer, and have very little impact on global warming. The use of a simple hydrocarbon, propane, as a refrigerant is becoming increasingly popular these days due to its high heat capacity and its short lifetime in the atmosphere. However, since propane is extremely flammable, it is prudent to minimize the amount of propane in the system in order to reduce the risks associated with leakage of the explosive gas. In this research, the possibility of reducing the mass of propane in the condenser without sacrificing the heat transfer capacity of the system has been investigated. In an air-conditioner or refrigeration system, condenser accommodates the most mass of the refrigerant compared with those in the other parts of the system. A MATLAB script has been developed which model the performance of a commercial portable air-conditioner. The results show that by increasing the working temperature of condenser from 30oC to 46oC at the ambient temperature of 27oC, about forty percent propane mass saving is achievable. These temperatures are still far below the critical (370oC) and auto-ignition (540oC) temperatures of propane

Impacts of room temperature on the performance of a portable propane air conditioner

The performance of a portable propane air conditioner system, in which the temperatures of the air passing over the condenser and evaporator are equal, has been experimentally investigated under different room temperatures and refrigerant charge levels. The research has been carried out in a range of room temperatures from 20°C to 35°C and in undercharge, standard charge and overcharge conditions. The results show that, at higher room temperatures, the refrigerant temperature in all parts of the system, the density of the refrigerant at the inlet and outlet of the condenser, mass of the refrigerant in the compressor, the mass flow rate of the refrigerant and the cooling capacity of the system in either the undercharge or full charge condition, the specific cooling capacity of the undercharge system, the useful work of the compressor, and the maximum pressure of the refrigerant increase. The increase in room temperature decreases the density of the refrigerant at the inlet and outlet of the capillary tube, the mass of the refrigerant in the capillary tube, the refrigerant subcooling at the inlet of the capillary tube, the maximum velocity of the refrigerant and the coefficient of performance. In addition, the increase in room temperature at overcharge condition causes an increase in the mass flow rate, cooling capacity and specific cooling capacity to a maximum value followed by their decrease. The most important difference between a portable air-conditioner and a non-portable system is the increase in cooling capacity with an increase in room temperature in full charge condition

Extending the capillary tube of a propane air-conditioner to reduce the refrigerant charge

Hydrocarbon refrigerants are employed to replace synthetic refrigerants due totheir low global warming and ozone depletion potentials; however, these refrigerants are flammable; therefore, their mass in the system should be minimized to reduce the associated risks. This study deals with the novelidea of extending the capillary tube of a portable air-conditioner in orderto decrease the amount of refrigerant charge in the system. Extending the length of the capillary tube will shorten thelength of the liquid line in applications in which the distance between theoutlet of the condenser and the inlet of the evaporator cannot be reduced. A script was developed and its accuracywas experimentally assessed.It was then used to estimate the amount of charge for the existing design and the extended capillary tube. The results show a significant reduction (63.9%) in the amount of propane in the capillary tubeand liquid line, and a reasonable decrease (8.3%) in the maximumspeed of refrigerant for the airconditioner used in this work

Modeling of Coal Spontaneous Fire in A Large-Scale Stockpile

The increasing need for energy consumption has resulted in the use of energy sources in coal continuing to increase. The transportation and distribution activities of coal also cause the pile to be exposed to heat when it is in a pile. Due to the kinetic characteristics of low-rank coal, the pile is very susceptible to spontaneous fire processes. Of course, this spontaneous fire phenomenon harms the safety and economic aspects of the coal pile. This study aims to model finite elements using Multiphysics simulation to determine the effect of the relative humidity of the pile on the temperature distribution of large-scale coal piles. Thus, handling methods and things that must be considered in storing and transporting coal piles can be formulated. Thermal phenomena modelling in coal piles is modeled using COMSOL Multiphysics software. The simulation is carried out by varying relative humidity of the environmental conditions (ambient). The simulation results show that this parameter can change the level of vulnerability of the pile to burn at an earlier time

MEMBANGUN MINAT BACA ANAK MELALUI POJOK LITERASI DI SDN 1 DESA DANAU PANTAU

Minat membaca di indonesia berada pada peringkat di bawah rata-rata, terutama para siswa-siswi di Desa Danau Pantau. Hal tersebut dikarenakan kurang memanfaatkan perpustakaan disekolah dan kurang koleksi buku bacaan. Karena hal itu, siswa-siswi di sekolah dasar SDN 1 Desa Danau Pantau kurang berminat membaca ke perpustakaan. Adapun pelaksanaan dalam kegiatan ini menggunakan metode  sosialisasi untuk meningkatan minat baca dan pemanfaatan perpustakaan yang dilakukan secara bertahap diantaranya, pembukaan dan pengenalan program, sosialisai pojok literasi dengan membaca yang dimulai dari buku-buku yang menarik minat baca siswa/siswi di SDN 1 Desa Danau Pantau. Hasil pengabdian kepada masyarakat mahasiswa KKN Kelompok 71 Danau Pantau yaitu, memberikan edukasi mengenai pentingnya minat  buku serta memanfaatkan perpustakaan dan meningkatkan minat  baca para siswa-siswi SDN 1 Desa Danau Pantau. Kegiatan ini dilaksanakan pada Agustus-September 2023 yang dihadiri oleh anak usia 7-8 tahun siswa kelas IV B. Kegiatan pojok literasi dilakukan secara bertahap diantaranya, pembukaan dan pengenalan program, sosialisasi pojok literasi dengan membaca dan menceritakan buku yang ada di Perpustakaan SDN 1 Desa Danau Pantau. Program KKN tersebut berjalan dengan lancar para siswa antusias ketika berkunjung ke perpustakaan

Highly transparent and antimicrobial PVA based bionanocomposites reinforced by ginger nanofiber

Good transparency, antimicrobial, physical, and tensile properties of the biodegradable film can be necessary for food packaging. The aim of this study is to characterize these properties of the poly(vinyl alcohol) (PVA)/ginger nanofiber (GF) bionanocomposite film. This nanofiber of 0.21, 0.31 and 0.41 g in suspensions, was mixed with PVA gel using ultrasonication. After addition of ginger nanofibers, the bionanocomposite film shows antibacterial activity but does not have antifungi activity. Increasing the nanofiber into PVA increases significantly in tensile properties, water vapour impermeability, and moisture resistance. Tensile strength, the temperature at maximum film decomposition, and moisture resistance (after 8 h) of the 0.41 g ginger nanofiber reinforced film were 44.2 MPa (increased by 65.6%), 349.4 °C (increased by 7%), and 6.1% (decreased by 18.7%), respectively compared to pure PVA. With this nanofiber loading, the transparency of the bionanocomposite film decreased slightly. These results suggest this bionanocomposite film has potential in food packaging in industrial applications

Dietary Intake of Methionine, Cysteine, and Protein and Urinary Arsenic Excretion in Bangladesh

BackgroundIn Bangladesh, millions of people are exposed to arsenic in drinking water; arsenic is associated with increased risk of cancer. Once ingested, arsenic is metabolized via methylation and excreted in urine. Knowledge about nutritional factors affecting individual variation in methylation is limited.ObjectivesThe purpose of this study was to examine associations between intakes of protein, methionine, and cysteine total urinary arsenic in a large population-based sample.MethodsThe study subjects were 10,402 disease-free residents of Araihazar, Bangladesh, who participated in the Health Effects of Arsenic Longitudinal Study (HEALS). Food intakes were assessed using a validated food frequency questionnaire developed for the study population. Nutrient composition was determined by using the U.S. Department of Agriculture National Nutrient Database for Standard Reference. Generalized estimating equations were used to examine association between total urinary arsenic across quintiles of nutrient intakes while controlling for arsenic exposure from drinking water and other predictors of urinary arsenic.ResultsGreater intakes of protein, methionine, and cysteine were associated with 10-15% greater total urinary arsenic excretion, after controlling for total energy intake, body weight, sex, age, tobacco use, and intake of some other nutrients.ConclusionsGiven previously reported risks between lower rates of arsenic excretion and increased rates of cancer, these findings support the role of nutrition in preventing arsenic-related disease

Intraperitoneal drain placement and outcomes after elective colorectal surgery: international matched, prospective, cohort study

Despite current guidelines, intraperitoneal drain placement after elective colorectal surgery remains widespread. Drains were not associated with earlier detection of intraperitoneal collections, but were associated with prolonged hospital stay and increased risk of surgical-site infections.Background Many surgeons routinely place intraperitoneal drains after elective colorectal surgery. However, enhanced recovery after surgery guidelines recommend against their routine use owing to a lack of clear clinical benefit. This study aimed to describe international variation in intraperitoneal drain placement and the safety of this practice. Methods COMPASS (COMPlicAted intra-abdominal collectionS after colorectal Surgery) was a prospective, international, cohort study which enrolled consecutive adults undergoing elective colorectal surgery (February to March 2020). The primary outcome was the rate of intraperitoneal drain placement. Secondary outcomes included: rate and time to diagnosis of postoperative intraperitoneal collections; rate of surgical site infections (SSIs); time to discharge; and 30-day major postoperative complications (Clavien-Dindo grade at least III). After propensity score matching, multivariable logistic regression and Cox proportional hazards regression were used to estimate the independent association of the secondary outcomes with drain placement. Results Overall, 1805 patients from 22 countries were included (798 women, 44.2 per cent; median age 67.0 years). The drain insertion rate was 51.9 per cent (937 patients). After matching, drains were not associated with reduced rates (odds ratio (OR) 1.33, 95 per cent c.i. 0.79 to 2.23; P = 0.287) or earlier detection (hazard ratio (HR) 0.87, 0.33 to 2.31; P = 0.780) of collections. Although not associated with worse major postoperative complications (OR 1.09, 0.68 to 1.75; P = 0.709), drains were associated with delayed hospital discharge (HR 0.58, 0.52 to 0.66; P < 0.001) and an increased risk of SSIs (OR 2.47, 1.50 to 4.05; P < 0.001). Conclusion Intraperitoneal drain placement after elective colorectal surgery is not associated with earlier detection of postoperative collections, but prolongs hospital stay and increases SSI risk

Reducing the mass of the refrigerant in the capillary tube of a propane air-conditioner

Hydrocarbon refrigerants are environmentally friendly and many countries have started using them in refrigeration and air-conditioner systems. Propane, a typical hydrocarbon, does not damage the ozone layer and its effect on global warming is very small. Use of propane as a refrigerant is gaining favour, especially in systems designed for R-22. The main drawback of using propane as a refrigerant is its flammability. To reduce the risk posed by propane, the total mass of propane in the system should be minimized without degrading the system performance. This work deals with how the mass of propane within a capillary tube can be reduced without compromising the system performance. In the first step, the mass flow rate and inlet and outlet conditions of the refrigerant within the capillary tube of a commercial propane air-conditioner under normal working conditions were measured. In the next step, a parametric MATLAB code was developed to determine the required length and volume of the capillary tube, and the velocity and mass of the propane within the capillary tube. The input parameters of the code are the inside diameter, roughness, shape, mass flow rate, and inlet and outlet conditions. The script was run for sixteen common types of capillary tubes, including the one in our laboratory. According to the results, it is possible to considerably reduce the propane mass within the capillary tube using a small inside diameter helical capillary tube with a decreased coil diameter. However, the results should not be extended to an air-conditioner in which the distance between the outlet of the condenser and the inlet of evaporator is fixed and longer than the calculated length

Performance of a single-duct portable propane air conditioning system under different refrigerant charge levels

The effects of the refrigerant charge on the performance of a portable propane air conditioning system have been evaluated and compared to nonportable systems in which the surrounding temperatures of the evaporator and condenser are not equal. This study aims to determine the similarities and differences in the performance of the two types of propane air conditioners under different charge levels, and to serve as a source of reference for future designs of portable air conditioners. The refrigerant charge was changed from −12.3% to +30% of its normal charge at several room temperatures ranging from 20°C to 35°C. The performance parameters include the refrigerant temperature, mass flow rate, maximum velocity of refrigerant, maximum pressure, cooling capacity, compressor work, specific cooling capacity, and coefficient of performance of the system. It has been found that an increase in charge level was found to increase the cooling capacity, coefficient of performance, and maximum velocity of refrigerant in the system while decreasing specific cooling capacity. The increase in the charge caused a relatively insignificant rise in the maximum pressure of the system and useful work of the compressor