Product Pull-Down Load
Heat to bring product to storage: above freezing Q = m cp deltaT.
Example
You enter
- Product mass (lb) 2000
- Specific heat above freezing (Btu/lb-F) 0.9
- Entering temperature (°F) 80
- Storage (target) temperature (°F) 35
- Pull-down time (hr) 24
You get
- Total heat to remove 81000
- Load rate 3375 Btu/hr
Checked against published worked examples from: Copeland.
Details, formula, and sources
ScopeFor a freezer add the latent heat of fusion and the frozen sensible. 2000 lb produce, cp 0.9, 80->35 F, 24 hr -> 81,000 Btu, 3,375 Btu/hr; freezing the same to 0 F -> 358,800 Btu (latent dominates). The product property tables govern.
Formula or tableabove freezing: Q = m cp (t_enter - t_storage); freezing: Q = m cp_above (t_enter - t_freeze) + m hif + m cp_below (t_freeze - t_storage); product entering at or below its freezing point: Q = m cp_below (t_enter - t_storage), no latent term; rate = Q / hours.
Source and editionThe product pull-down (cooling and freezing) load with the latent heat of fusion, from ASHRAE Refrigeration, by name.
Free accessThe sensible-plus-latent product-cooling load is standard published refrigeration practice; the property tables are in the ASHRAE Handbook - Refrigeration.
What governsEstimate. AHJ and licensed professional govern.
API field namesmass_lb, cp_above, t_enter_f, t_storage_f, hours, q_btu, rate_btuh
- Sensible above freezing Q = m cp (t_enter - t_storage)calorimetry
- Freezing add sensible-to-freezing + m x hif + frozen sensible belowASHRAE Refrigeration
- Property tables specific heats, freezing points, and latent heats from ASHRAEscope of this tile