01511nas a2200121 4500008004100000245006100041210006100102300001400163490000700177520110400184100002601288856007501314 2002 eng d00aComputational Aspects of Nodal Multizone Airflow Systems0 aComputational Aspects of Nodal Multizone Airflow Systems a1083-10900 v373 aThe multizone approach to steady-state airflow problems models a building as a network of discrete mass flow paths. A nodal formulation of the problem writes the governing equations in terms of the unknown pressures at the points where the flow paths connect. This paper proves conditions under which the nodal equations yield symmetric positive-definite matrices, guaranteeing a unique solution to the flow network. It also establishes relaxed conditions under which a nodal airflow system yields asymmetric matrices with positive eigenvalues, guaranteeing at least one solution. Properly exploiting the system properties greatly reduces the cost of numerical solution. Thus, multizone airflow programs such as Contam and Comis depend on symmetric positive-definite systems. However, the background literature neglects or simplifies the underlying assumptions, does not assert existence and uniqueness, and even contains factual errors. This paper corrects those errors, states the implicit assumptions made in the programs, and discusses implications for modelers and programmers.1 aLorenzetti, David, M. uhttps://eta.lbl.gov/publications/computational-aspects-nodal-multizone