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Pham Quang Vu,Kwang-Il Choi,Jong-Taek Oh 대한설비공학회 2018 대한설비공학회 학술발표대회논문집 Vol.2018 No.11
The use of HCFCs refrigerants is gradually being replaced by HFCs and hydrocarbons refrigerants that have zero ODP (Ozone Depletion Potential). R-290 (propane) is a hydrocarbon refrigerant with C3H8 molecular structure. In this research, the flow condensation heat transfer occurs inside an aluminum multiport mini-channel tube with 0.83㎜ of hydraulic diameter. In order to determine the value of heat transfer coefficient, the experiment was carried out for mass fluxes ranging from 50㎏/㎡s to 500㎏/㎡s, heat fluxes ranging from 3㎾/㎡ to 12㎾/㎡, and saturation temperatures of 48℃. the condensation heat transfer coefficient of propane is influenced by vapor quality, mass flux, and heat flux. A new correlation for condensation heat transfer coefficient was developed with present experimental data.
Single-phase heat transfer and pressure drop characteristics in multiport mini-channel tubes
Pham Quang Vu,Kwang-Il Choi,Jong-Taek Oh,Honggi Cho 대한설비공학회 2017 대한설비공학회 학술발표대회논문집 Vol.2017 No.6
The single-phase heat transfer and pressure drop in multiport mini-channel tubes were measured using water as the working fluid. Two different multiport tubes were used to obtain experiment heat transfer coefficient and frictional pressure drop with varying of Reynold number from 50 to 10.000. The inlet and outlet temperatures, the wall temperatures along the test section, the pressure drop and the mass flow rate were measured. The relationships between the mass flow rate, the heat flux on the pressure drop and heat transfer coefficient were analyzed. Also, the empirical correlation for heat transfer coefficient and pressure drop adjusted from the experimental data are proposed.
Pham, Duong Quang,Ba, Duong Thi,Dao, Nga Thu,Choi, Gyung Ja,Vu, Thuy Thu,Kim, Jin-Cheol,Giang, Thi Phuong Ly,Vu, Hoang Dinh,Le Dang, Quang Elsevier 2017 INDUSTRIAL CROPS AND PRODUCTS Vol.108 No.-
<P><B>Abstract</B></P> <P>The antimicrobial efficacies of extracts and constituents fractionated from <I>Rheum tanguticum</I> rhizomes were evaluated by using <I>in vitro</I> and <I>in vivo</I> bioassay against seven phytopathogenic fungi and ten pathogenic bacteria, respectively. Dichloromethane and ethyl acetate soluble extracts derived from <I>R. tanguticum</I> rhizomes effectively controlled plant diseases caused by five fungi <I>Magnaporthe oryzae</I>, <I>Blumeria graminis</I> f. sp<I>. hordei, Colletotrichum coccodes, Phytophthora infestans,</I> and <I>Puccinia recondita</I> in <I>in vivo</I> whole plant bioassay. In addition, these extracts showed strong inhibitory activity against the bacterial growth of <I>Acidovorax avenae</I> subsp. <I>cattlyae</I> (Aac), <I>Clavibacter michiganensis</I> subsp. <I>michiganensis</I>, <I>Xanthomonas arboricola</I> pv. <I>pruni</I> (Xap), and <I>Pseudomonas syringae</I> pv. <I>actinidiae</I> (Psa), with MIC values ranging from 125 to 250μg/mL. The active extracts of <I>R. tanguticum</I> rhizomes were fractionated by using various and repeated chromatographic techniques to yield seven constituents that included three anthraquinones and four stilbenes. Notably, at concentrations ranging from 75 to 300μg/mL, physcion (<B>DH03</B>) and chrysophanol (<B>DH04</B>) were significantly effective in suppressing the development of barley powdery mildew (BPM) caused by <I>B. graminis</I> f. sp. <I>hordei,</I> with control values from 80 to 96.7%. Moreover, stilbenes rhapontigenin (<B>DH02</B>) and desoxyrhapontigenin (<B>DH05</B>) had a broad spectrum and potent activity against phytopathogenic bacteria; <B>DH05</B> effectively inhibited the bacterial growth of Aac, <I>Burkholderia glumae</I> and Psa at MICs ranging from 38 to 150μg/mL. In this paper, we report their antibacterial activity for the first time. The botanical materials containing anthraquinones and stilbenes were active against both phytopathogenic fungi and bacteria. These results suggested that <I>R. tanguticum</I> rhizomes could be used as a new source of antimicrobial substances for developing a botanical fungicide and bactericide to control plant diseases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>R. tanguticum</I> extracts exhibited activity against phytopathogenic fungi and bacteria. </LI> <LI> Seven anthraquinones and stilbenes from <I>R. tanguticum</I> were isolated and identified. </LI> <LI> <I>In vivo</I> antifungal activity of botanicals was evaluated by the whole plant bioassay. </LI> <LI> The isolated stilbenes effectively inhibited the growth of phytopathogenic bacteria. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Experimental investigation of flow condensation in the micro-fin tube
Pham Quang Vu,Kwang-Il Choi,Jong-Taek Oh,Honggi Cho 대한설비공학회 2018 대한설비공학회 학술발표대회논문집 Vol.2018 No.6
This study experimentally investigated the flow condensation heat transfer characteristics of R410A, R22, R32 and R290 (propane) inside a 7mm OD micro-fin copper tube. The flow condensation heat transfer was measured at mass fluxes of 50 to 380kg/m2s; heat flux of 3 and 12kW/m2; and a saturation temperature of 48oC. The variations of refrigerant mass flux, heat flux with condensation heat transfer performances were obtained. The comparison shows that the heat transfer coefficients of propane are higher than those for R32, R22 and R410A. The different thermophysical properties of the four refrigerants result in the heat transfer coefficient differences.