A. Specification of example

To illustrate the design of a shell-and-tube heat exchanger with twisted tubes, a case is presented for a heat exchanger system for wine liquor cooling in a wine production plant with a throughput 2,000 litres per hour. In this heat exchange system, countercurrent flow of the hot and cold streams is used; thus the wine liquor flows inside the tubes and the cooling medium (a 21% aqueous solution of calcium chloride, “CaCl₂ brine”) flows in the space between the tubes. The temperature of the CaCl₂ brine at the heat exchanger inlet is -6 ± 2 °C. The wine liquor enters the heat exchanger with a temperature +12 ± 2 °C and has to be cooled down to -2 ± 1 °C. The pressure drop has to be less than 5 × 10⁴ Pa. To facilitate cleaning, a modular design was selected for the system. Thus, a system consisting of 8 modules, connected by branch pipes, allowing one or more of the modules to be disconnected and cleaned whilst the other modules remained in operation. The modules are mounted on a frame and each module consists of a shell containing a bundle of 7 oval twisted tubes fastened into tube plates. Mutual contact between the twisted tubes (see Figure 386.1) ensures suppression of tube vibration (Dzyubenko, 1980).

(a) Calculation method

The total surface areas for heat transfer is defined as

\[\label{eq1} S_{warm} =Nl_{\Sigma}\pi d_{mean}, \tag{1}\]