## 5 Conclusions  
The design of a large-diameter EAHX for standalone use, capable of removing office room loads in hot and dry climates, is a very challenging task. However, using monitoring data from an existing large-diameter EAHX, this paper confirmed that, in spite of the challenge, a graph-based method relying on simplified analytical expressions can assist in this design.  
Using monitoring data it was concluded that:  
* With adequate sizing, large-diameter EAHX can remove significant room loads without the need for refrigeration machines and with little electrical energy consumption. For the monitored EAHX, a total peak cooling capacity of 28 kW and a total of 330 kWh removed in a day were achieved with just 50 kWh/day of fan electricity consumption. As regards specifically the EAHX's ability to remove room loads--essential to assess the standalone cooling capability, a maximum value of 22 kW was monitored, i.e., the EAHX is capable of offsetting 49 W/m\({}^{2}\) of the room cooling demand.
* Still, these results are only possible when an adaptive standard for thermal comfort is considered. Indeed, regarding the choice of the design room setpoint temperature, use of adaptive comfort models allowing setpoints higher than those for conventional HVAC systems is, most likely, mandatory when designing an EAHX for standalone use.
* Moreover, for the hottest summer days, the monitoring data showed that for hours with outdoor temperature equal to 37 \({}^{\circ}\)C (meeting the design condition criteria), room load removal in the EAHX reached, at best, 60% of the design cooling demand. As it happens in the design of naturally ventilated office buildings for hot and dry climates, the adoption of (building-related) passive cooling techniques, such as combining the use of building thermal mass with forced nighttime ventilation, is, most likely, also mandatory when designing an EAHX for standalone room cooling.
* Concerning the graph-based design method, the monitoring results obtained considering the design conditions were fairly matched by those determined from the graphs and from the analytical expressions supporting the graphs. This confirms that simplified analytical expressions and graphical methods can assist designers seeking an EAHE alternative to conventional HVAC solutions based on refrigeration machines.  
This paper addressed heat-transfer-related challenges in large-diameter EAHX design; however, a designer has to overcome many non-heat-transfer obstacles to justify the adoption of this type of EAHX for standalone room cooling. From the authors' experience, winning decision makers' trust in large-diameter EAHX cooling capabilities is a major challenge, justifying the need for continued research and dissemination of post-occupancy monitoring data.  
Conceptualization, R.D.; Methodology, R.D. and A.M.R.; Formal analysis, A.M.R. and M.d.G.G.; Investigation, R.D.; Resources, F.P.; Data curation, F.P.; Writing--original draft, R.D.; Writing--review & editing, R.D., A.M.R. and M.d.G.G.; Project administration, M.d.G.G.. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
The first author acknowledges the Portuguese Foundation for Science and Technology (FCT) for funding the research unit MARE (UIDB/04292/2020). The second and fourth authors acknowledge the Portuguese Foundation for Science and Technology (FCT) for funding the research unit CERIS (UIDB/04625/2020).  
The authors declare no conflicts of interest.