me2016, your posts lack in detail and what you have posted doesn't really make much sense.
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[li]How do you expect to control the space temperature/humidity (read: space conditions) without A/C?[/li]
[li]You offered a summer ambient temperature, bud didn't provide a winter condition. depending on the climate, maintaining these conditions could be much harder in the winter than in the summer (you may need humidification)[/li]
[li]somehow I doubt the humity is 70% year-round. The only environment this might be plausible is in the tropics and in that environment the 45 degC temperature is unlikely.[/li]
[li]what is the usage of the space? dry storage? is there any heat/moisture load? are there large doors to the outside? are these doors frequently open?[/li]
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I apologise if this come across as a bit abrupt, but you have to understand that if you want useful answers to your questions you have to provide the right level of data for educated responses.
You need an industrial sized dehumidifier and/or Outside Air unit. Exactly what you need will depend greatly on warehouse location, size and available space for the new equipment.
Engage a local engineer's services for best results.
Where is the warehouse and what items will be stored in the warehouse? Will the conditioning be for people comfort only or will it also be for the items stored? Is there a separate room for people and people. Is air conditioning required only in the people room and the warehouse need only ventilation and heating?
As others had mentioned, you need to invest in some infrastructure for this endeavor. Your design winter condition is 21°C (or 70°F) and 30% RH. This is a 37°F dew point.
You can achieve the temperature and humidity requirements via heating and humidification. The outdoor airflow value would be needed to determine how much heating and humidification is needed.
Your design summer condition is 27°C (81°F) and 40% RH. This is a 54.5°F dew point. You would need to cool any incoming ventilating (outdoor) air to about 55°F to achieve this. If that supply temperature will over-cool the space, reheat would be desirable.
this is packaging warehouse where used to store the CARTONS that we use it for milk and to get good sealing we should store it in temperature between 21 to 27 degree.C and RH between 30% to 40% for five days(this requirement from carton supplier)
from 2016 monitoring we note the RH above the target all the year but the temperature sometimes in the range sometimes above and sometimes below
Knowing that last bit of info now, you really need to seal up the warehouse good, or at least a portion, and install a good HVAC system to keep temperature and humidity within that range.
This is something that cannot be thrown together. You need a properly designed system and set of contols. The changes you need to make will be significant and require building department approval. If you have not already done so, hire an architect and HVAC engineer.
it's all about the Outside and inside condition of the system. If you want to understand clearly just take a psychrometric chart and make the outside and inside points and make a process. then you will know wheater you need humidification or dehumidification to bring the desired RH % for that temp.
A good HVAC engineer is what you need. Based on the location he can know the outdoor design conditions summer and winter. He would know how to calculate cooling, heating, dehumidification, humidification and ventilation loads based on the building orientation and design, based on the amount of material stored, the number of people. What energy and medium to use for heating, etc.
for the calculation i will hire HVAC company but i'd like to understand the process and the right solution
please what is best to use rooftop units or chiller with AHU's
your explanation and advice are highly appreciated
Rooftop units will most likely be the more cost effective system, depending on the overall load and site constraints of course. A good HVAC engineer should be able to discern the best solution for the application.
