Functional Design of the mCCHP-RES System - Design for Micro-Combined Cooling, Heating and Power Systems - page 264

The following variables represent the operating parameters of a hydraulic circuit
when it is intended to carry thermal energy:
Q

Heat ow (kW);

ow (m 3 /h); V Volume

Temperature difference ( o C); D#

fluid (kg/m 3 ); q Density of thermal

Ho Pressurization pressure of the thermal fluid (Pa);

c Speci c heat capacity of the thermal fluid (kWh/kg ° C);

v Flow velocity (m/s).

In circuit sizing, the required values of operating parameters are known from
the beginning, as there are among the technical characteristics of those components
of the system mCCHP that the circuit connects them. Connection is only possible if
these values are the same for all connected components.
At the same time, the required values of operating parameters represent the input
dataset in the circuit sizing problem.
Sizing of such hydraulic circuit requires the following steps:

(a) The circuit establishing This consists of establishing the site of each element
that is placed on the circuit, and choosing the appropriate pipelines (including
the pipe and

fittings).

For example, the pipe is chosen according to the required internal diameter,
which can be determined using the equation:

s

V
v

DN ¼ 4 ; 6 ð mm Þ ð 38 Þ

where:
DN Internal diameter (mm),
V Volume flow (Ltr/min),

v Flow velocity (m/s).

Note:

1. In order to minimize the pressure loss through the pipe, it is recommend that the

flow velocities
between 0.4 and 1 m/s should be used, resulting in a pressure drop of between 1
and 2.5 mbar/m pipe length.
2. It is possible to determine the volume

flow velocity through the pipe should not exceed 1 m/s. Ideally,

flow with the equation :

Q

V

m 3 ¼ = h ð 39 Þ

q c D#