成果報告書詳細
管理番号20140000000466
タイトル*平成25年度中間年報 「高効率ノンフロン型空調機器技術の開発 冷媒の性能、安全性評価 エアコン用低GWP冷媒の性能および安全性評価」(H23-H27)
公開日2014/8/20
報告書年度2013 - 2013
委託先名国立大学法人東京大学
プロジェクト番号P11008
部署名環境部
和文要約ノンフロン型空調機器用冷媒の性能評価と安全性評価をするために、下記研究項目を実施した。
東京大学担当:
(1)エアコンの性能評価法の確立
・エアコン、ビル用マルチエアコンの部分負荷特性と快適性評価の検討
・低GWP冷媒の熱交換器性能,サイクル性能の評価
(2)室内への冷媒リーク時の安全性評価
・微燃性冷媒が室内へ漏洩したときの濃度分布の解析
・熱分解、燃焼後のHF濃度解析
・リスク評価
産総研担当:
(3)ノンフロン型冷媒の実用条件の燃焼性評価
・R1234yfと数種の可燃性ガスの二元混合系の燃焼限界
・R32と冷媒関連化合物との混合系の燃焼性
・R1235yfの熱分解及び生成物分析
(4)ノンフロン型冷媒の着火エネルギー評価法の開発
・消炎距離、消炎直径の評価
英文要約(1) University of Tokyo
In this study, diffusion phenomena were numerically analyzed when a mildly flammable refrigerant leaked from a room air conditioner, a variable refrigerant flow (VRF) or a chiller into a large space where these were equipped. From the calculation results, the refrigerant concentration distributions, the volumes and positions of the flammable regions, and their changes in time were discussed. (a)For the leakage from wall-mounted indoor unit, combustion does not occur if the ignition source does not exist inside the indoor unit. (b)For the leakage from floor-mounted indoor unit, safety regulations are required for when flammable refrigerants are used in air conditioners. (c)For the leakage from outdoor unit, considering drain and under cut, presence time is shorter and the flammable volume time (FVT) is lower. (d)For the leakage from floor-mounted indoor unit and outdoor unit, the risk of R1234yf is higher than R32. (e)For the leakage from VRF, considering burning velocity, FVT is much smaller. (f)For the leakage from water-cooled chiller, the ventilation air flow has a big effect on the FVT. When there is no ventilation air flow and the velocity of refrigerant leakage is high, the FVT might be increase after refrigerant completely leaks out. (g)The experiment confirmed that the concentration on the floor does not reach LFL for the leakage from the wall-mounted indoor unit and exceed UFL for the leakage from the floor-mounted indoor unit.
This study was carried out to quantify HF, the main toxic product, and to analyze other products in the thermal decomposition of refrigerants. For R32, R1234yf and R134a, lower limit temperatures of thermal decomposition and amount of products were measured in the way less-affected by wall materials.
(2) AIST
The flammability limits for binary mixtures of R1234yf with methane, R152a, R143a, R32, and carbon monoxide were measured in dry air. The measurements were made using the ASHRAE method. As a result, it has been found that the flammability limits deviate from the values predicted by Le Chatelier’s law if the counterpart gas molecule contains more hydrogen atoms than fluorine atoms.
We have introduced a new index of F2-number, which is a square of normalized flammable range and approximately represents the strength of combustion power. In order to assess the suitability of R32 as the reference gas, we measured the flammability limits of binary mixture of R32 with each of several flammable and non-flammable gases.
Effects of R1234yf concentration and total flow rate on thermal decomposition of R1234yf/air mixture have been investigated using a flow reactor. The decomposition of R1234yf was observed at a certain temperature, and the decomposition rate was considerably increased at this temperature. The major products were HF, COF2, CO2, and CO, and the amounts of productions such as HF and O2 consumption were increased with increasing decomposition of R1234yf. It has been found that when the total flow rate increases, the decomposition temperature rises.
In parallel plate quenching distance measurement, we prepared larger apparatus than previously used in order to obtain the reliable quenching distances for 2L refrigerants using larger parallel plates. By using the larger plates we obtained the converged quenching distances for 2L refrigerants and their concentration dependence. From these data, the minimum ignition energy was estimated on the basis of a heat loss theory. We also obtained a good correlation between the quenching distance and the mass burning rate, which is the product of the burning velocity and the unburned gas density.
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