Environmental Engineering Reference
In-Depth Information
Covering the swimming pool during the night can reduce the heat losses
by about 40-50 per cent.
The heat demand
(3.56)
of a swimming pool can then be estimated by considering the difference
between the losses and the solar radiation gains over the operating period
t
tot
.
In moderate climatic regions (e.g. central Europe), the heat demand of a
swimming pool without a cover and at a base temperature of 23°C is about
300 kWh/m
2
per season. This demand can be provided easily by a solar
heating system. The solar absorber size should be 50-80 per cent of the pool
surface; however, these values can vary significantly. Therefore, simulations
with professional computer programs can provide more exact values.
H
EAT
D
EMAND AND
S
OLAR
F
RACTION
The heat demand
Q
D
of domestic water systems can be calculated from the
amount of water taken. With the heat capacity of water [
c
H
2
O
= 1.163
Wh/(kg K)], the taken water mass m, the cold water temperature
ϑ
CW
and the
warm water temperature
ϑ
HW
, the heat demand becomes:
(3.57)
Table 3.13 shows typical values for the
hot water demand
in residential
buildings in Germany. If no value for the cold water temperature is given, a
value of
ϑ
CW
= 10°C can be used. In countries with higher annual ambient
temperatures, a higher cold water temperature should be chosen. If washing
machines or dishwashers with hot water inlets are used, the hot water demand
increases.
Table 3.14 shows typical values for the
hot water demand of hotels
, hostels
and pensions. The hot water demand of restaurants can be estimated as
230-460 Wh/ per set menu and of saunas as 2500-5000 Wh/user.
Table 3.13
Hot Water Demand of Residential Buildings in Germany
Hot water demand in
Specific heat content in
litres/(day and person)
Wh/(day and person)
ϑ
HW
= 60°C
ϑ
HW
= 45°C
Low demand
10-20
15-30
600-1200
Average demand
20-40
30-60
1200-2400
High demand
40-80
60-120
2400-4800
Source:
VDI, 1982
