【正文】 cture, mature techniques and wide applicability, which make it widely utilized in various industries [ 1 ].The baffle element plays very important roles in STHX,such as supporting the tube bundles and disturbing the fluidof shell side. According the direction of fluid flow of shellside, the STHX can be divided into three groups: transverse flow, longitudinal flow and helical flow. The characteristicsof pressure drop and heat transfer in shell side of the STHX vary under different flow states, which have a heavy impacton the performance of the heat exchangers.The traditional shellandtube heat exchanger with segmental baffles (SBSTHX) have many disadvantages, such as high pressure drop, low heat transfer efficiency, harmful vibration caused by the shellside flow which is normal to tube bundles. When the traditional segmental baffles areused in STHX, higher pumping power is often required tooffset the higher pressure drop under the same heat , a new type of STHX using different types of baffles might achieve higher heat transfer efficiency and lower pressure drop. Pressure drop and heat transfer are two interdependent factors influencing the capital and operating costs of the heat exchange systems. In order to improve the performance, heat exchangers with different types of baffles are developed, which have relatively higher heat transfer efficiency and relatively lower pressure drop,such as rod baffles and helical baffle exchangers [ 2 – 11]. Therefore, the main objectives of this study are to develop an STHX with new type of baffles to overe the deficiencies mentioned above and to experimentally investigate its performance. Moreover, performance of the new STHX is also pared with that of SBSTHX in this study.The dimension of the heat exchanger isU159 mm 95 mm. The detailed parameters of heat exchangers are shown in Tables 1 and 2 .2 Configuration and fabrication of the STHX with new type of bafflesThe helical type of fluid flow in shell side of the STHX with helical baffles has led to some advantages such as high heat transfer efficiency and low flow resistance [ 5 , 6 , 8 ]. Nevertheless, it is difficult to manufacture the continuous helical baffles. In order to address this problem, flowerbaffles STHX (FBSTHX), a new type of STHX based on the traditional segmented baffle, is proposed in this paper and shown schematically as in Fig. 1 . As seen in Fig. 1 ,around baffle can be divided into four quadrants, and among the four quadrants, at least one quadrant is hollow for fluid flowing, and the remaining quadrants are used to support the heat tube. As the flower baffles are installed alternately, the phase angles (the angles for hollow parts of the two adjacent baffles) can be 30,60 ,or90 . Under different application situations, the phase angles may vary. From Fig. 1 it can also be observed that the configuration of all baffles in FBSTHX is the same。 only the phase angles are different. As a result, the manufacturing process for the flower baffles is considerably simplified. The fabricating process of the flower baffles is the same as that of segment baffle, and the flower baffles are fixed by tension rods. In the present FBSTHX, there are four tension rods to fix the baffles. Figures 2 and 3 schematically show the stream line for the fluid flow over the segmental baffles and the flower baffles respectively. From the figures, it can be observed that the fluid flow in shell side for SBSTHX is zigzag and the fluid flow in shell side for FBSTHX is longitudinal with some swirling which will lead to some difference of heat transfer and flow resistance about these two type of STHXs. In this paper, the shellside local heat transfer coefficients of FBSTHX were obtained experimentally and pared with that of SBSTHX.4 Data acquisitionsIn the experiments, the flow rate, temperature, and pressure drop were measured. The energy imbalance between the shell side and the tube side was calculated from the data on the flow rates, and the inlet and the outlet temperatures both in shell and tube sides. The heat balance was conSide red to be achieved when the energy imbalance is less than 5%. Based on the energy balance between the shell and tube side, the overall heat transfer coefficient of the STHX can be calculated. The tube side heat transfer coefficient can be calculated using the classical correlation, so the shell side heat transfer coefficient can be obtained using the overall heat transfer calculation correlation. The overall pressure drop can be directly measured. So the correlation between the friction factorf, Nusselt number Nu and Reynolds Recan be obtained. The detailed procedures are presented as follows.The overall heat transfer coefficient for heat exchangerscan be puted using Eq. 1 [ 12]where hi, heat transfer coefficient for tube side, W/(m2K)。ho , heat transfer coefficient for shell side, W/(m2K)。 R i,fouling coefficient for tube side, (m2K)/W。 R o, fouling coefficient for shell side, (m2K)/W。 R w, thermal resistance for tube wall, (m2K)/W.Since the heat exchangers in our experiments are newlyfabricated, the effects of the two fouling resistance are negLigible. Therefore, the above equation can be expressed asBased on the transfer correlation, the overall heat transfer coefficient can be achieved asWhere Q, the average heat flux between the cold and the hot fluid, W。 A , heat transfer area based on the tube out diameter, m2, which can be calculated using Eq. 4 .N, tube number。 do, tube out diameter, m。 L , effective length of tube, m。 Dtm, logarithm averaged temperature for the cold and the hot fluid, C The heat exchanger is double tube passes and one shell pass, and the logarithm averaged temperature difference can be stated as [12]where in and out temperature for tube side fluid, in and out temperature for shell side fluid, C.Heat transfer between cold and hot fluid can be achieved according t