Handbook of air conditioning and refrigeration / Shan K

LOAD CALCULATIONS 6.43
● Load. In the load phase, all external and internal heat gains are calculated. The heat gain profile is
then converted to a cooling load profile.
● Design. In the design phase, based on the maximum block space sensible load, the volume flow
and the size of the air system are determined from the psychrometric analysis. In design phase it
also calculates the coil’s load and selects the size of the coils.
● System. In the system simulation, the program predicts the load that is imposed on the equipment
according to the space load profile and the type of air system selected.
● Equipment. In the equipment (plant) phase, the energy consumption of the fans, furnaces or boilers,
and refrigeration systems is determined based on the hourly coil loads.
● Economic. During the economic analysis, utility cost is calculated from the energy use. When it
is combined with installation cost and maintenance cost, a life cycle cost is available for
comparison.
Only the load calculation program is covered in this section. The available documentation for
TRACE 600 includes User’s Manual, Engineering Manual, Quick Reference, Cook Book, Software
Bulletin—Getting Started, etc.
The hardware requirements for TRACE 600 are as follows:
Personal computer
Hard disk
Ram requirement
DOS Version 3.1 or higher
IBM AT 286 processor or higher
Program: 7.5 Mbytes hard disk space (3 M
bytes for load calculation)
Job: 3 to 10 Mbytes depending on the size of
job
640 kbytes
The TRACE 600 data sheet can be created by using the input editor. The input file is organized
in card format. In each input card, every input is shown by a given field. Sometimes, the value and
unit of input are separated into two fields. Entering the inputs can be done either by using field
mode or by using full-screen mode. In field mode, the user can access help and selection to determine
and select a specified input. Field mode input is preferable. In full-screen mode, the user can
view a full screen of raw input. Each line shows the inputs of a card and is prefixed by a twocharacter
code. Each field in a card is separated by a forward slash.
Input data are subdivided into five groups: job, load, system, equipment, and economic. Many
input cards and fields inside the input cards are optional, i.e., may be left blank.
Trace 600 Input—Load Methodology
In TRACE 600, card 10 lists various methods of cooling and heating load calculations for the user’s
selection. There are five cooling load calculating methods:
● CEC-DOE2. This method adopts the transfer function method for both heat gain and space cooling
load calculations. The space load calculations adopt the precalculated weighting factors listed
in DOE 2.1 Engineering Manual. This is a comparatively exact cooling load and energy calculation
method, especially for air systems operated at nighttime shutdown mode. CEC-DOE2 needs
more computational calculations. However, it is often not a primary problem when the computations
are performed by a powerful PC.
● CLTD-CLF. This method also adopts the transfer function method for both heat gain and space
cooling load calculations. Cooling load temperature difference (CLTD) and cooling load factor
(CLF) tables are prepared based on the exact transfer function coefficients or weighting factors