**Brice Rogie \*, Wiebke Brix Markussen, Jens Honore Walther and Martin Ryhl Kærn**

Department of Mechanical Engineering, Technical University of Denmark, Nils Koppels Allé, Building 403, 2800 Kongens Lyngby, Denmark; wb@mek.dtu.dk (W.B.M.); jhw@mek.dtu.dk (J.H.W.); pmak@mek.dtu.dk (M.R.K.)

**\*** Correspondence: brogie@mek.dtu.dk; Tel.: +45-45-25-41-21

Received: 14 October 2019; Accepted: 4 December 2019; Published: 11 December 2019

**Abstract:** The present study investigated a new microchannel profile design encompassing condensate drainage slits for improved moisture removal with use of triangular shaped plain fins. Heat transfer and pressure drop correlations were developed using computational fluid dynamics (CFD) and defined in terms of Colburn j-factor and Fanning f-factor. The microchannels were square 2.00 × 2.00 mm and placed with 4.50 mm longitudinal tube pitch. The transverse tube pitch and the triangular fin pitch were varied from 9.00 to 21.00 mm and 2.50 to 10.00 mm, respectively. Frontal velocity ranged from 1.47 to 4.40 m·s−1. The chosen evaporator geometry corresponds to evaporators for industrial refrigeration systems with long frosting periods. Furthermore, the CFD simulations covered the complete thermal entrance and developed regions, and made it possible to extract virtually infinite longitudinal heat transfer and pressure drop characteristics. The developed Colburn j-factor and Fanning f-factor correlations are able to predict the numerical results with 3.41% and 3.95% deviation, respectively.

**Keywords:** microchannel; evaporator; water drainage; heat transfer; pressure drop; CFD
