This simulator compares two fin-and-tube heat exchangers — an evaporator coil absorbing heat from indoor air and a condenser coil rejecting heat plus compressor input to outdoor air — at fixed refrigerant saturation temperatures, so you can study the air-side heat balance without a full refrigerant-cycle model.
• Equipment laboratory tab: a real-time 3D cutaway of the evaporator coil, indoor blower, drain pan/frost layer, compressor heat contribution, condenser coil, outdoor fan, expansion-device context, and high-side liquid/low-side vapor lines, with Home view, Focus selected part, Show full enclosure / cutaway, Exploded view, Auto rotate and Expand camera controls plus a clickable, numbered component list with callouts. Controls include evaporating and condensing saturation temperature, evaporator and condenser entering air temperature, evaporator and condenser air volume flow, compressor heat input, coil conductance loss (fouling), and an Enable subfreezing frost accumulation checkbox, alongside live stats, a What is happening? sequence readout, operating-history chart, switch-state tokens and a cell-readings table. • Curves & measurements tab: a heat-transfer duties chart (heat absorbed, available rejection, required rejection), a leaving-air temperatures chart (evaporator and condenser leaving air), the model equations, and snapshot measurement readouts. • Experiments tab: four preset investigations (clean coils baseline, outdoor airflow restricted, dirty fins, subfreezing evaporator with frost) plus a Run model checks verification bench and a timestamped event log with trial-report export. • Learn & assess tab: lesson cards on the two-exchanger heat balance, air heat capacity, fouling effects and reading a rejection deficit, a knowledge-check quiz with reset, and a scope/references note.
The evaporator coil absorbs sensible heat from indoor air as it passes over cold refrigerant-filled tubes; the condenser coil rejects heat from hot refrigerant to outdoor air. Because refrigeration is a heat pump, the heat the condenser must reject equals the heat the evaporator absorbs plus the compressor's shaft/electrical input — energy conservation across the whole cycle.
Each exchanger is modeled with an air-side heat-capacity rate (mass flow × specific heat) and an effectiveness set by its UA (overall conductance × area), so absorbed or rejected heat follows Q = ε·Cair·ΔT. Fouling and, below freezing, an imposed frost layer reduce the effective UA even when airflow is unchanged. Because saturation temperatures are fixed rather than solved from a refrigerant property table, the model reports a rejection deficit — required rejection minus available condenser duty — as a diagnostic when the fixture cannot close the heat balance, rather than inventing a new condensing pressure.
The heat-transfer duties chart plots heat absorbed by the evaporator, the condenser's available rejection, and the required rejection (evaporator duty plus compressor input) side by side; a positive rejection deficit on the stats panel means the condenser cannot currently reject everything the cycle demands at the fixed temperatures and flows you've set. The leaving-air temperatures chart shows how much the evaporator cools indoor air and how much the condenser warms outdoor air, both governed by Q = ṁ·cp·ΔT.
The Run model checks button in the Experiments tab exercises independent fresh models — leaving your current trial untouched — to confirm relationships like higher fouling reducing both exchanger duties and increased compressor input raising the rejection requirement. This is a sensible-only air model with fixed saturation temperatures and no refrigerant property table, full-cycle mass-flow solution, latent/condensation calculation, or moisture-deposition physics for frost — it is a teaching fixture, not a manufacturer coil-selection tool.
It models the air side of two fin-and-tube coils — an evaporator and a condenser — at fixed refrigerant saturation temperatures using ρair = 1.2 kg/m³, cp = 1.006 kJ/(kg·K), and UA values of 2.5 kW/K (evaporator) and 3.5 kW/K (condenser) before any degradation. It does not solve a refrigerant property table, mass flow, or valve dynamics.
Because a refrigeration cycle is a heat pump: the compressor adds shaft/electrical energy to the refrigerant, and by energy conservation the condenser must reject the evaporator heat plus that compressor input. The simulator calculates this required rejection directly.
With saturation temperatures fixed rather than solved, if the condenser cannot reject as much heat as is required at the current airflow, fouling and outdoor temperature, the simulator reports the shortfall as a rejection deficit — a diagnostic signal, not a real operating state a real system would reach (it would instead shift pressures or trip).
Enabling subfreezing frost accumulation applies an imposed, time-based conductance loss on the evaporator once its saturation temperature is below 0°C, gradually lowering its effective UA. It is an illustrative degradation, not a moisture-deposition or defrost-cycle calculation.