A Fast Method for Evaluating a Simplified Hot Dry Rock Heal. Flow Problem

Abstract

I present optimizations to the computation of Elsworthís single zone, hot dry rock thermal recovery model. These enhancements lead to as much as a 6-fold increase in computational speed. The greatest time savings derive from an efficient evaluation of the modelís thermal response due to a step in heat flux, which is required for solution of the more general problem via Duhamelís Principle. Further enhancements come from taking advantage of the special structure of the modelís finite difference equation. Reductions in execution speed were sought in order to facilitate the modelís implementation on AT-class microcomputers. The PC-based application requires multiple evaluations of the model. Typical execution times on a. 33 MHz 80386 microcomputer for 128 time steps were 7 seconds, as compared with 25--42 seconds for the non-optimized approach, and for 512 time steps were 28 and 100-168 seconds, respectively; the timing of the non-optimized method depended upon particulars of the dimensionless variables.