Evaluation of performance an air conditioning systems using t-junction flash gas refrigerant
The purpose of this study was to determine the performance of air-cooled chiller system using T-junction flash gas bypass refrigerant. The experiment was conducted by installing T-junction after expansion device to separate the phase of refrigerant liquid and gas which flows to the evaporator. The working fluid is used as a cooling medium is R-290. To get performance data, measurements performed at the time of steady state when the water chilling temperature T = 15 C up to T = 10 C and flow rates kept constant at 1 GPM (6.3 x 10-5 m3/s). Finally, the use of T-junction mode in AC system generates an increase in the refrigerating effect and coefficient of performance systems (CoP) by 6% and 17.8 %, respectively. Also, it can decrease the heat of compression by 8.5%. This has implications for the lighter compressor work and saving the power consumption of the AC system.
R-1270 Vapor Compression Refrigeration Performance Study
Received 07/12/2020 revision 21/04/2021 accepted 22/05/2021 Available online 30/05/2021 This study aims to obtain performance data on the vapor compression refrigeration system using R-1270. Refrigerant R-1270 classify as a hydrocarbon refrigerant (HC) that is environmentally friendly. This refrigerant has a value of ODP = zero and GWP <3. The Tests were conducted on a vapor compression refrigeration system that consisted of a domestic refrigerator (RD) and a chest freezer (CF). The parameters measured in this research were: refrigeration effect, compression work, the weight of refrigerant circulated, electricity consumption, coefficient of performance, and the time required to reach the lowest evaporator temperature. The first test was to used R-134a as a baseline refrigerant with the mass as the manufacturer recommends. Then, the second step was to test the performance of the vapor compression refrigeration system that used R-1270 with 30 % of the baseline mass. The test was conducted for 300 minutes by recording the observed data at every 30 minute interval. The results showed that the replacement of baseline refrigerant by R-1270 increase the coefficient of performance of the vapor compression refrigeration system by 13 % 56 %. It also reduces electricity consumption by 13.5 % 19 %. This research has implications for the work of compressors that becomes easier and cheaper energy costs.
Case study: performance effectiveness and cost-benefit analyses of open-graded friction course pavements in Tennessee
Abstract The effectiveness and cost-benefit of Open-Graded Friction Course (OGFC) pavements were analysed in this study by investigating the cost, field performance, short- and long-term effectiveness, and accident rate of OGFC projects in Tennessee. Paired sample t-tests were conducted to compare if there was significant difference between OGFC and non-OGFC sections. Investigation on the performance effectiveness showed that OGFC sections provided comparable performance level as traditional dense mix overlays and were effective in improving pavement performance and repairing deterioration except for rutting potential. However, no severe pavement deterioration was observed on the OGFC sections after more than four or five years of service, indicating sufficient durability of the OGFC used in Tennessee where mild freeze-thaw cycles are experienced annually. Although the unit cost ($/m3) of OGFC was about 42% higher than the cost of traditional dense mix overlays, it was observed that the accident rate was significantly reduced especially in rainy days after the OGFC treatment. The cost-benefit analyses based on the ratio of accident rate reduction over cost demonstrated that OGFC was significantly more cost-beneficial in improving driving safety and reducing accident rate in rainy days.