( ( The ( coolant ( phase change ) ) ) ( ( ( keeps ( ( the boards ) ( at ( ( essentially constant ) temperature ) ) ) ) ( without ( ( the bulk ) ( of chillers ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ coolant) (NN phase) (NN change)) (VP (VBZ keeps) (NP (NP (DT the) (NNS boards)) (PP (IN at) (NP (ADJP (RB essentially) (JJ constant)) (NN temperature)))) (PP (IN without) (NP (NP (DT the) (NN bulk)) (PP (IN of) (NP (NNS chillers)))))) (. .)))
The coolant phase change keeps the boards at essentially constant temperature without the bulk of chillers.
(ROOT (S (PP (IN During) (NP (NN phase) (NN change))) (, ,) (NP (NP (DT the) (NN temperature)) (PP (IN of) (NP (DT a) (NN system)))) (VP (VBZ remains) (ADJP (JJ constant))) (. .)))