This paper investigates the internal flow and heat transfer in chevron shaped plate heat exchanger with the conjugate heat transfer model developed by commercial computational fluid dynamics (CFD) software. This chevron plate heat exchanger consists of a stack of corrugated plates in mutual contact, and hot and cold channels are positioned between the intermediate chevron solid plates. The chevron plate has been studied for proper experimental correlations of heat transfer and pressure drop [1, 2], the design optimization of chevron plate [3] and numerical simulation of small sized plate [4]. And, two types of welded plate heat exchanger are examined by CFD analysis [5]. The turbulent model and wall function of chevron plate are suggested by comparing several turbulent models [6]. The purpose of this study is to describe heat transfer in detail, considering conjugate heat transfer between fluid and solid domains through the chevron plate. The fluid domain includes hot and cold channel, and the solid domain similarly contains solid chevron plates. As the internal flow and heat transfer in the chevron plates is not easily converged in the CFD solving process, the practicable conjugate heat transfer model are required and developed. The corrugated plate with 14 chevron shapes is designed for sufficient length. Each fluid and solid domain is properly meshed by grid independent test. The working fluid is water and counter flow configuration is adopted. The CFD model is simulated in Reynolds number range from 1,000 to 9,000 by CFD analysis with Realizable k-ε model. The distributions of temperature and surface heat transfer coefficient are displayed as simulation result in Fig. 1. The average heat transfer coefficient and Nusselt number calculated from CFD analysis are compared with the various empirical correlation data [1] in Fig. 2. Fig. 1: Temperature and Surface heat transfer coefficient on chevron plates; (a,b) in hot channel, (c,b) in cold channel.

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We studied the transient local surface temperature response that occurs when jet impinging of nitrogen gas is applied to the surface to which a pulsating heat flux is applied. After manufacturing a micro jet impinging device, which was composed of three parts--a silicon wafer, a vinyl sticker, and a Pyrex wafer--nitrogen gas was used as working fluid and the velocity was 344.8 m/s, corresponding jet Reynolds was 1467. And the amplitudes of heat fluxes varied from 5.67 to 16.17 W/cm 2 , the frequency also varied from 0.1 to 1000 Hz, then temperature response of RTDs was acquired. For example, when a heat flux, 8.5 W/cm 2 , was applied with a frequency of 0.1 Hz, the highest and lowest temperatures of RTD located on the center of the heater and under indirect jets were 30.2 °C and 20.7 °C. From the acquired results, the time constant of the device was estimated between 17 ms and 32 ms, and this result shows the conjugated mode of conduction and convection of heat transfer. To understand the dominant heat transfer, we decoupled the conduction mode and the convective heat transfer mode through analytical calculations and confirmed that the time constants were 11 μs and 128 ms, respectively. In addition, the heat transfer coefficient was inversely calculated through numerical calculation by simulating the RTD manufactured in the device, and through this, it was confirmed that the dimensionless time constant was related to the Nu number and the correlation was developed as / t τ − = ≤