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Copy file name to clipboardExpand all lines: _posts/2021-09-07-design-of-the-koji-room-koji-muro.md
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@@ -113,8 +113,7 @@ This is a 1-dimensional heat transfer problem. If we pick 4-inch polyurethane wi
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If the indoor conditions are maintained at 30°C, we can further demonstrate that the heat losses through the wall will total **764W**. To keep the room warm, an equal amount of heat must be supplied. Let's illustrate the conditions of the koji room at time t=0 after inoculation, during which the koji generates no heat and all openings to the room are closed:
*Heat balance of the koji room immediately after inoculation*
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### 3. Ventilation
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First, consider the requirements for **heat removal**. We can show that our 300kg of rice-koji at *hiki-komi* has a dry weight of 195kg, and will generate 1623W at the peak of its metabolism (see Appendix - Step 4). Our conductive heat losses were calculated to be 764W, so we know that ventilation for heat removal must equal 859W by exchanging indoor air with cold, outdoor air. This requires a ventilation rate of 41m³/h.
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*Heat balance of the koji room with ventilation sized for heat removal*
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Next, let's consider the requirements for **moisture removal**. About 80% of the heat generated by koji is lost as water vapour, with the remaining 20% lost due to other effects. At the peak of its heat generation, we can show that the our 300kg of koji will emit 2.16kg of water per hour (see Appendix - Step 5). By exchanging moist indoor air with dry, outdoor air, we can show that a ventilation rate of **119m³/h** is necessary to remove the moisture emitted by koji.
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*Mass balance of the koji room with ventilation sized for moisture removal*
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Finally, let's consider the requirements for **carbon dioxide removal**. Koji has a respiratory coefficient of around 1.0 throughout its entire process, which means that the koji's peak heat generation of 1623W equates to a CO₂ generation rate of 0.3m³ CO₂/h (see Appendix - Step 6) using the aerobic metabolism equation:
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If we maintain an indoor carbon dioxide concentration at 4500ppm, which is 500ppm below the OSHA Permissible Exposure Limit (PEL = 5000ppm), and assume an outdoor CO₂ concentration of 500ppm, we can show that the flow rate necessary to remove all generated carbon dioxide is **76m³/h.**
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*Mass balance of the koji room with ventilation sized for carbon dioxide removal*
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Comparing the three ventilation rates, we can see that **moisture removal**, at 119m³/h, is the limiting design criteria in our scenario.
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### 4. Heating
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Knowing that our maximum ventilation rate will be **119m³/h**, let's size the heating panels of the koji-room. Our conductive heat losses are 764W, and ventilating fresh air at 119m³/h removes 2480W of heat. Our koji generates 1623W of heat at its peak, so our heater must provide at least 1621W of heat (see Appendix - Step 7):
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*Final heat balance the koji room with ventilation with ventilation sized for moisture removal*
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And that's it! At t=0h, our heaters will be running at 764W and our ventilation turned off; and at the peak of growth, our heaters will be running at 1459W and our ventilation at 119m³/h. This is our operating window, and every other point in time will fall somewhere between these two extremes. Achieving steady conditions is the job of whatever **control system** we select. This can range from a basic thermostat and humidistat to a programmable controller.
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