Abstract: The experimental thermal performance of two heat
exchangers in closed-wet cooling tower (CWCT) was investigated in
this study. The test sections are heat exchangers which have multi path
that is used as the entrance of cooling water and are consisting of
bare-type copper tubes between 15.88mm and 19.05mm. The process
fluids are the cooling water that flows from top part of heat exchanger
to bottom side in the inner side of tube, and spray water that flows
gravitational direction in the outer side of it. Air contacts its outer side
of that as it counterflows. Heat and mass transfer coefficients and
cooling capacity were calculated with variations of process fluids,
multi path and different diameter tubes to figure out the performance
of characteristics of CWCT.
The main results were summarized as follows: The results show this
experiment is reliable with values of heat and mass transfer
coefficients comparing to values of correlations. Heat and mass
transfer coefficients and cooling capacity of two paths are higher than
these with one path using 15.88 and 19.05mm tubes. Cooling capacity
per unit volume with 15.88mm tube using one and two paths are
higher than 19.05mm tube due to increase of surface area per unit
volume.
Abstract: In this study, we experiment on precise control outlet
temperature of water from the water cooler with hot-gas bypass
method based on PI control logic for machine tool. Recently, technical
trend for machine tools is focused on enhancement of speed and
accuracy. High speedy processing causes thermal and structural
deformation of objects from the machine tools. Water cooler has to be
applied to machine tools to reduce the thermal negative influence with
accurate temperature controlling system. The goal of this study is to
minimize temperature error in steady state. In addition, control period
of an electronic expansion valve were considered to increment of
lifetime of the machine tools and quality of product with a water
cooler.