论文标题
热平衡方法中的因果关系问题用于计算设计加热和冷却负载
Causality issue in the heat balance method for calculating the design heating and cooling load
论文作者
论文摘要
基于动态模型的加热和冷却负载计算被广泛用于仿真软件中，这是Ashrae和Cen推荐的方法。原则是使在均匀温度下考虑的房间空间的空气体积的热量平衡，并从该方程式计算负载，即获得所需的室内温度所需的功率。问题在于，这样做不尊重身体因果关系。如果模型通过分段线性动力学系统近似，则此过程会导致不正确的传输函数。为了指出此问题，引入了一种从热网络中获取状态空间和传输函数模型的方法。然后，采用传输函数表示形式表明改变物理因果关系会导致不当传递函数。实际的结果是，当空间温度变化时，如果仿真时间步长倾向于零，则计算的负载趋于无穷大。因果关系问题可能是基于方程式的仿真软件（例如Modelica）的问题，其中方程不代表因果关系：平衡方程中因果关系的错误选择可能会导致不当传输功能。
Heating and cooling load calculation based on dynamic models is widely used in simulation software and it is the method recommended by ASHRAE and CEN. The principle is to make the heat balance for the air volume of a room space considered at uniform temperature and to calculate from this equation the load, i.e. the power needed to obtain the required indoor temperature. The problem is that, by doing so, the physical causality is not respected. If the model is approximated by a piecewise linear dynamical system, this procedure results in an improper transfer function. In order to point out this problem, a method to obtain state space and transfer function models from thermal networks is introduced. Then, the transfer function representation is employed to show that changing the physical causality results in an improper transfer function. The practical consequence is that when the space temperature has a step variation, the calculated load tends to infinity if the simulation time step tends to zero. The issue of causality may be a problem in equation-based simulation software, such as MODELICA, in which the equations do not represent causal relations: a wrong choice of the causality in a balance equation may result in improper transfer functions.
