追焚運転と給湯負荷特性を考慮したCO_2ヒートポンプ式給湯機の性能評価に関する研究

摘要

This paper describes a performance evaluation of CO_2 heat pump (HP) water heaters. We evaluated the influence of reheating operation and domestic hot water (DHW) load characteristics on the system performance. First, we carried out experiments by using the modified M1 mode for the DHW and reheating loads. The great differences about the control of the output hot water temperature of the HP unit, and the amount of hot water storage etc. are confirmed under the reheating operation compared with results of the modified M1 mode only. In the reheating operation, SCOP is lower than the value for the modified M1 mode by approximately 30% in winter. Secondly the Hot water whose amount of heat was equivalent to the reheating load was taken in a bathtub. Although differences in operation control compared to the modified M1 mode were not detected, the hot water supply temperature fell below 60℃ several times. Within around 40% decrease or increase compared with the standard hot water usage, there were almost no differences on the operation control. SCOP at the lower hot water load fell below the standard. Therefore, it is necessary to consider a DHW usage model appropriate for the amount of a DHW load.%本論文は，高効率の貯湯式給湯システムとして普及が進んでいるCO_2ヒートポンrnプ（Heat Pump：HP）式給湯機の2008年機を対象に追焚運転，給湯負荷特性などがrnシステム性能に及ぼす影響について評価を行ったものである．まず，修正M 1モードrnに追焚負荷を加えた実験を実施し，HP出湯温度，残湯量などの制御に大きな差異がrn生じることを確認した．追焚負荷を考慮した場合のSCOPは，修正Mlモードにおけrnる値と比較して，冬期に約30％の低下が見られた．次いで，追焚負荷に相当する熱rn量を差湯運転で賄った場合には，制御への影響は生じないものの，給湯温度が60℃rnを下回る場合も見られることを確認した．標準湯使用量に対して，約4割減～4割rn増の範囲においては，制御への影響はほとんど見られないが，少人数家族を想定しrnた場合にはSCOPが低下することから，湯消費に応じた給湯負荷モードを用いて評価rnする必要がある．