12/13/2015

HVAC Water Chillers Chiller Configurations CHILLER SYSTEM

HVAC Water Chillers
Chiller Configurations CHILLER SYSTEM


MULTI CHILLER SYSTEMS




THE SINGLE-CHILLER SYSTEM:

The basic chilled water piping configuration for a single chiller is shown in Figure 2.1. Here, a single chiller provides chilled water to the cooling coils utilizing a single chilled water pump.
For small systems, this configuration has the advantage of lower initial cost, but does have some basic disadvantages:

1. With the single-compressor system, failure of any component (compressor, pump, or condenser) will result in no cooling being available. For most facilities, this is unacceptable and the use of multiple chillers allows at least some cooling (50% or more) be provided even if one chiller fails. In cases where cooling is critical to the facility (computer centers, hospital, laboratories, pharmaceutical or textile manufacturing, etc.), multiple chillers with at least one redundant chiller are often used. In this case, even if one chiller fails, 100% of the design cooling load can still be met.

2. As discussed in Chapter 1, once the cooling load imposed on a rotary compressor chiller falls to below about 30% of the chiller capacity, theefficiency of the chiller begins to decline. Thus, the use of multiple chillers allows a better overall capacity-to-load ratio and improved operating efficiency.

MULTI CHILLER SYSTEMS:

For multiple chiller systems, there are two basic configurations that can be utilized,series or parallel flow. 
In a series configuration with two chillers, as shown in Figure 2.2, each chiller is selected to produce half of the required cooling at the full system flow rate.Thus, half of the total design range is produced by each chiller. Load ratios other than 50/50 are possible, but this is by far the most common condition because of 
control problems with chillers at very small temperature differences.
Table 2.1 summarizes the temperatures at various load conditions for the configuration shown in Figure 2.2.
Series chiller systems are rarely utilized in present times because this configuration requires a constant chilled water flow rate at all times, resulting in high pumping costs. But, if a relatively large temperature difference is required or if there is a very steady base cooling load, the series configuration may offer some advantages.

Constant flow, single chiller configuration.

The parallel chiller configuration is far more common. In a two-chiller configuration, each chiller is typically selected to operate with the same design range, but with only a half of the total system flow requirement. This again results in a 50/50 load split, but other load ratios may be selected if dictated by operational requirements. And, there is no real limitation on the number of parallel chillers that can be utilized in one system.

Series chiller configuration.

Series Configuration Temperatures

younes kandi




















0 comments:

Post a Comment