Deterministic Building Science and Thermodynamic Modeling Framework for Real-Time Field Diagnostics, Air Distribution, and Decarbonization Sizing

Abstract

Modern heating, ventilation, air conditioning, and refrigeration (HVAC/R) engineering workflows are frequently constrained by legacy software architectures, subscription-gated paywalls, unverified heuristics, and invasive data-tracking mechanisms. This paper presents HVACLogic, an open-access, client-side, deterministic computational framework engineered for high-precision building load estimation, duct hydraulic sizing, psychrometric state determination, and refrigeration circuit diagnostics. By implementing the foundational physical models of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), the Air Conditioning Contractors of America (ACCA), and the Sheet Metal and Air Conditioning Contractors' National Association (SMACNA) within an immutable, client-side execution environment, HVACLogic guarantees sub-millisecond evaluation latency, 100% offline operational capability on remote jobsites, and complete privacy preservation with zero project-data exfiltration. We outline the mathematical derivations governing fluid friction (Colebrook-White and Huebscher circular equivalency), multi-variable moist air psychrometrics, zeotropic refrigerant phase transitions (R-454B, R-32, R-410A temperature glide), and multi-layer envelope thermal conductance. Cross-validation against ASHRAE Fundamentals golden datasets demonstrates numerical concordance within 0.05%. Open-access computational framework and interactive calculation suite available at: https://hvaclogic.org