Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Causality issue in the heat balance method for calculating the design
  heating and cooling load   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.

24
The categories of this paper are: dg-ga
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin
8
The categories of this paper are: hep-ex
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
7
The categories of this paper are: hep-th
2
The categories of this paper are: math
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas