Cooling Systems Tool

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Description


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Description:

Different cooling configurations can quickly be entered and compared, so that an informed choice of the appropriate system combination is possible. Simplicity of use and instant display of results supports the workflow.

User:

The primary target group for the tool are designers of cooling systems. The tool is kept comparatively simple, so that it can also be helpful when coordinating the work of, among others, architects and mechanical systems engineers

Input:

For a particular month: ambient and indoor conditions, cooling demand and treated floor area of the building.

Properties of the ventilation system.

Properties of the respective cooling/dehumidification system, such as airflow rate, on/off or inverter operation, cooling capacity and energy efficiency ratio

Output:

Sensible and latent cooling demand, contribution of each system, and resulting total electricity consumption. Determination of whether the selected system is able to cover both the cooling and dehumidification demand.

Strength:

Different cooling configurations can quickly be entered and compared, so that an informed choice of the appropriate system combination is possible. Simplicity of use and instant display of results supports the workflow.

Challenge:

The tool does not provide a detailed, hourly simulation of the behaviour of a cooling system in interaction with the building or with detailed control strategies.

Outcome:

In addition to the existing methodology of the PHPP 9 software, which was used as the basis for development, the “Cooling Systems Tool” has the following features:

• Contemporary split units usually use so-called inverter technology, a compressor that can vary its capacity between 100% and, depending on the system, 10 to 60%. Below this limit the units are operating in on/off mode. The tool accounts for this behaviour.

• The sensible capacity of supply air cooling can be enhanced by recirculating additional indoor air over the cooling coil. Alternatively, if required, an internal heat exchanger (e.g. a wrap-around heat pipe) can reduce the sensible heat ratio to provide sufficient dehumidification. Such systems are currently being developed by manufacturers and are now represented in the tool. They can result in significant cost reductions because the functions of ventilation, heating, cooling, dehumidification, and possibly hot water production are integrated in one single unit.

• A detailed calculation of the energy efficiency ratio is implemented for all cooling methods.

• Stand-alone dehumidifiers typically release their waste heat (generated from the condensation process and electricity consumption) to the room. In most cases this will lead to an increased sensible cooling demand, which in turn increases the dehumidification by the cooling system. A thorough review of the existing analytical solution showed that it provides the best possible estimate.

• Split units or fan-coils can usually operate with different ratios of airflow and cooling power. For low airflow volumes the dehumidification capacity is high, but the sensible cooling capacity is lower than rated. For high airflow volumes the full sensible cooling capacity is available, but little dehumidification is provided. In the tool the user is able to enter two different operation modes. The tool automatically chooses the most appropriate mode for providing the cooling and dehumidification required at the lowest possible energy demand.

• An important input for the analysis of supply air cooling is the airflow rate. Whilst it can be assumed to be constant for residential buildings, there will be intermittent operation in many non-residential applications. This changes the behaviour of the system, particularly the dehumidification performance. The tool takes into account how many hours per day and days per week the system is operating.

• The operating time also affects the part load ratios of the systems and possibly the contribution of each system to the total cooling demand.

Format:

Microsoft Excel and operates under Microsoft Windows