its driving heat from a motor co-generation unit and is
specially designed for weather conditions with high
humidity ratios of the ambient air. A pilot system has
been installed in fall 2003 at the client building of the
gas utility of the municipality of Palermo (AMG) in Sic-
ily/Italy and the system is commissioned and operated
with accompanying monitoring during 2004.
2. Desiccant air handling unit configuration
As a first step of the project different configurations
of desiccant air handling units were compared in order
to identify the configuration which is able to provide de-
sired supply air conditions with a minimum of energy
consumption. However, before the different new designs
are presented and compared, the standard desiccant
cycle as used in temperate climates is described in detail
in order to show the general operation principle. Based
on this cycle different modifications were made in order
to adjust it to the specific needs in a warm-humid
climate.
2.1. Standard desiccant cooling cycle
The standard cycle which is mostly applied today uses
rotating desiccant wheels, equipped either with silica gel
or lithium-chloride as sorption material. All required
components are standard components and have been
in use for air-conditioning of buildings or factories since
many years.
The standard cycle using a desiccant wheel is shown
in Fig. 1 and the corresponding states of the air in the
cycle are shown in Fig. 2. Systems according to thisscheme are typically employed in temperate climates;
the example of Fig. 1 is based on typical design condi-
tions in Central Europe (e.g. Germany). The air follows
the following processes during the system:
1 ! 2 sorptive dehumidification of supply air; the
process is almost adiabatic and the air is heated
by the adsorption heat and the hot matrix of
the wheel coming from the regeneration side;
2 ! 3 pre-cooling of the supply air in counter-flow to
the return air from the building;
3 ! 4 evaporative cooling of the supply air to the
desired supply air humidity by means of a
humidifier;
4 ! 5 the heating coil is used only in the heating sea-
son for pre-heating of air;
5 ! 6 a small temperature increase is caused by the
fan;
6 ! 7 supply air temperature and humidity are
increased by means of internal loads;
7 ! 8 return air from the building is cooled using
evaporative cooling close to the saturation line;
8 ! 9 the return air is pre-heated in counter-flow to
the supply air by means of a high efficient
air-to-air heat exchanger, e.g. a heat recover
wheel;9 ! 10 regeneration heat is provided for instance by
means of a co-generation system;
10 ! 11 the water bound in the pores of the desiccant
material of the dehumidifer wheel is desorbed
by the hot air;
11 ! 12 exhaust air is blown to the environment by
means of the return air fan.
Application of the cycle described above is limited to
temperate climates. Reason is, that the achievable sup-
ply air dehumidification is not high enough to enable di-
rect evaporative cooling at conditions with far higher
values of the humidity of ambient air.
3. Cycles adjusted to humid climates
For all studied cycles the same boundary conditions,
i.e., temperature and humidity values of ambient air,
supply air to the building, return air from the building
and regeneration air to regenerate the sorption material
were assumed. These values are shown in Table 1. The
following modified cycles which all use cooling coils in
addition to the sorptive wheel were studied regarding
their energy performance:
• Standard cycle with a cooling coil added behind the 室内空调英文文献和中文翻译(2):http://www.751com.cn/fanyi/lunwen_14819.html