Visualization study of a loop heat pipe with two evaporators and one condenser under gravity-assisted condition

摘要

In this work, the thermofluid behavior of a loop heat pipe (LHP) with two evaporators and one condenser was experimentally investigated. Acetone was used as the working fluid. To directly investigate the flow patterns and vapor-liquid distribution, visualization tests were conducted in the condenser, evaporator cores, and compensation chambers (CCs) of the MLHP with a variety of heat loads. The experiments were conducted under a gravity-assisted condition (i.e., the condenser was positioned 360 mm higher than the evaporators). Under the normal operating pattern, both evaporators were heated; for the heat load sharing pattern, only one of the evaporators was heated. To conduct visualization tests, the condensing tube of the MLHP was fabricated using a transparent plastic pipe. In each CC of the MLHP, a glass tube was installed. These tests investigated a combination of temperature variations, pressure drops, vapor-liquid distribution and two-phase flow regions. In the normal operating pattern and heat load sharing pattern, the relation between heat leak and two-phase length in the condenser was confirmed. The effect of gravitational head on flow patterns in the condensing tube and heat leak were also investigated. In the heat load sharing pattern, visualization experiments were used to study the vapor-liquid distribution in each evaporator core and CC. In the gravity-driven mode, a lack of heat load sharing was discovered and investigated. In the gravity-capillary codriven mode, nucleate boiling was observed in the unpowered evaporator core. (C) 2019 Elsevier Ltd. All rights reserved.