This case study has an important role in demonstrating the coupling of the spreadsheets of EN ISO 52016-1, EN 17898-7 and EN 17898-5-1, in order to represent the effects different control strategies for an air conditioning system. The most important aspects demonstrated here arethe mechanism of required and actual operational values such as air flow rates or supply air temperatures.

 Two situations are calculated, and for each , a summer and a winter week is analysed:

 

1. A load dependent variable volume flow rate with pre-defined supply temperature:
The required volume flow rate is calculated in order to meet the cooling or heating needs of the zone. The system operation follows that required value as within its boundaries, set by the maximum design volume flow rate of the system and the minimum possible operation at 20%. The supply air temperature is pre-defined by an outdoor temperature dependent curve.

Conclusions: The results for both summer and winter show that the required cooling or heating needs lead to high required air volume flow rates on some days. The actual air volume flow rates follow these required values except for peak situations, where the required flow rates exceed the maximum flow rate of the system. Accordingly, the cooling or heating needs are not met during these times.

2.  An air quality dependent 2 stage volume flow rate with load dependent control of the supply temperature:

The required volume flow rate is calculated in order to meet the air quality requirements depending on the occupation in the thermal zone, representing a CO₂-dependent control with a control inaccuracy. The system operation follows that required value by switching between 100% and 66% of this value so that the value is always above the required value. The required supply air temperature is calculated in order to meet the cooling or heating needs of the zone. The system operation follows that required value as within its boundaries.

Conclusions:
The results for both summer and winter illustrate that the supply air volume flow rate shows the 2 stage operation of the system, which follows the occupation schedule. The required cooling or heating needs lead to low or high required supply air temperatures at some times. The actual supply air temperatures follow the required values, except for the peak situations, where they reach the limit. Accordingly, the cooling or heating needs are not met during these times.

 

This Case Study is restricted to a few specific parameter settings for an air conditioning system.. The results show the expected behaviour of the thermal zone under the influence of the ventilation systems, and vice versa. The order of magnitude of the calculated variables is applicable in a real situation.

You can find the full document at the link below:Report Case Study on EN 16798-7 and EN 16798-5-1 Mechanical Ventilation