This Code provides methods and procedures for testing single phase heat exchangers. The Code presents and describes the methods for determining heat exchanger performance, for measuring fluid conditions and related phenomena, and for projecting performance parameters to reference conditions. Performance parameters included are overall heat transfer coefficient, heat transfer rate, and pressure drop. Guidelines are provided for recommended instrumentation and accuracy. The scope of this Code includes instruments, calculation techniques, and methods to determine the steady state performance of single phase heat exchangers at both test conditions and reference conditions. This Code applies to, but is not limited to, the following types of heat exchangers: (a) Shell-and-tube; (b) Plate-frame; (c) Plate-fin; and (d) Tube-in plate fin. Single-phase fluid streams, including liquid-to- liquid, gas-to-liquid, and gas-to-gas are included. Excluded from this Code are heat exchangers used in condensation, vaporization, fired, direct contact, non-newtonian fluid, and more than two-fluid applications. Supplementary information is included on (a) Steady state criteria; (b) Equations and coefficients for uncertainty analysis; (c) The Delaware Method for shell-side performance; (d) Mean temperature difference; (e) Derivation of performance equations; (f) Tube-side performance methods; (g) Fouling resistance; (h) Plate frame performance methods; (i) Thermal physical properties; (j) Room cooler performance methods; and (k) Examples.