A novel shell-and-tube heat exchanger with screw cinquefoil orifice baffles is designed to grasp the weakness of the traditional shell-and-tube heat exchanger with cinquefoil orifice baffles. It specifically enhances the heat transfer coefficient in the area between adjacent baffles and enhances the shell-side fluid flushing ability on bundles. In the proposed shell-and-tube heat exchanger with screw cinquefoil orifice baffles, screw-type cinquefoil orifice baffles are installed in the shell side. Shell-and-tube heat exchanger with screw cinquefoil orifice baffle is compared with shell-and-tube heat exchanger with cinquefoil orifice baffles and the traditional shell-and-tube heat exchanger with segmental baffles by means of numerical simulations. The numerical result shows that the heat transfer coefficient and shell-side fluid flushing ability in the shell-and-tube heat exchanger with screw cinquefoil orifice baffle is higher than that in the shell-and-tube heat exchanger with cinquefoil orifice baffles and shell-and-tube heat exchanger with segmental baffles, for the shell-side fluid that is urged to flow in approximately continuous helical flow. Under the same shell-side mass flow rate, heat transfer coefficient of shell-and-tube heat exchanger with screw cinquefoil orifice baffle is about 9.2% higher than that of shell-and-tube heat exchanger with cinquefoil orifice baffles and shell-and-tube heat exchanger with segmental baffles by about 5.4% on average. The article presents a novel design thought when researchers design heat exchangers.
Settled dust is an important medium
for semivolatile organic compound
(SVOC) transport indoors. Understanding the mechanism of interaction
between SVOCs and settled dust can greatly improve the exposure assessment.
This study develops an analytical model to elucidate the mechanism
of direct contact between SVOC sources and settled dust. The model
incorporates the adsorption of SVOCs onto indoor surfaces, which was
ignored in previous numerical models. Based on this model, a hybrid
optimization method is applied to determine the key parameters of
SVOC transport, i.e., the diffusion coefficient in the dust, the dust–air
partition coefficient, and the chamber surface–air partition
coefficient. Experiments of direct contact between SVOC source materials
containing organophosphorus flame retardants (OPFRs) and settled dust
were conducted in chambers. The key parameters were determined by
performing curve fitting using data collected from the OPFR chamber
tests and from the literature on phthalates. The reliability and robustness
of the model and measurement method are demonstrated by the high fitting
accuracy and sensitivity analysis. The obtained key parameters are
more accurate than those from correlations in prior studies. Further
analysis indicates that dust–air partition coefficient plays
an important role and the adsorption effect on surfaces cannot be
neglected for SVOC transport.
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