INTRODUCTION When a fluid flows through a coiled pipe the effect of the centrifugal forces is to superimpose a secondary flow onto the primary (axial) flow@ acting in a plane perpendicular to the pipe axis. As a result of the secondary flow there is an increase in the rates of forced convective heat@ mass and momentum transfer (and hence pressure drop) over the values obtained in a similar straight pipe. This Item presents heat transfer data for the flow of single-phase Newtonian fluids in coils and is complementary to Item No. 77029 (Derivation 42) which can be used to calculate the corresponding pressure drop data; the two Items are generally compatible both in notation and terminology. The data presented are for helical coils but some guidance is given for non-helical coils (see Section 8); the types of coils considered in this Item are defined in Appendix A. Under some circumstances (see Section 5) curvature effects may be neglected and a realistic calculation of heat transfer in coils can be made using straight pipe data. Heat transfer data for flow in straight pipes may be obtained from Item Nos 92003 and 93018 (Derivations 43 and 44). The data for helical coils are given in the form of Nusselt numbers@ Nu@ based on circumferentially averaged heat transfer coefficients@ ?? @ and the effects of the following parameters are considered: (i) Reynolds number@ Re@ (ii) Prandtl number@ Pr (iii) diameter ratio of the coil@ D/d@ (iv) pitch ratio of the coil@ s/D. In most cases the data in this Item may be expected to provide values of heat transfer coefficient accurate to within ?? 20 to 25 per cent@ but Appendix B and Table 13.1 discuss the accuracy and derivation of the data in greater detail. Information on the applicability of the data is given in Section 3. A Flow Chart (Section 14) is included as a guide to the use of this Item.
ESDU 78031 A-1998 history
1998ESDU 78031 A-1998 INTERNAL FORCED CONVECTIVE HEAT TRANSFER IN COILED PIPES