(1)解法一:Q 吸=cm(t-t0) =4.2×10 3J/(kg·℃)×100kg×(50℃-20℃)=1.26×10 7J
解法二:Q 吸=cm△t =4.2×10 3J/(kg·℃)×100kg×30℃=1.26×10 7J
(2)
=8400s(140min、2.33h);
(3)
;
(4)节能、环保
(1)解法一:Q 吸=cm(t-t0) =4.2×10 3J/(kg·℃)×100kg×(50℃-20℃)=1.26×10 7J
解法二:Q 吸=cm△t =4.2×10 3J/(kg·℃)×100kg×30℃=1.26×10 7J
(2)
=8400s(140min、2.33h);
(3)
;
(4)节能、环保