diff --git a/src/lagrangian/coalCombustion/submodels/surfaceReactionModel/COxidationDiffusionLimitedRate/COxidationDiffusionLimitedRate.C b/src/lagrangian/coalCombustion/submodels/surfaceReactionModel/COxidationDiffusionLimitedRate/COxidationDiffusionLimitedRate.C
index e86391182f..7e8f2a0e2b 100644
--- a/src/lagrangian/coalCombustion/submodels/surfaceReactionModel/COxidationDiffusionLimitedRate/COxidationDiffusionLimitedRate.C
+++ b/src/lagrangian/coalCombustion/submodels/surfaceReactionModel/COxidationDiffusionLimitedRate/COxidationDiffusionLimitedRate.C
@@ -143,7 +143,7 @@ Foam::scalar Foam::COxidationDiffusionLimitedRate::calculate
     dMassSRCarrier[CO2GlobalId_] += dmCO2;
 
     // Heat of reaction [J]
-    return HcCO2_*dmCO2;
+    return -HcCO2_*dmCO2;
 }
 
 
diff --git a/src/lagrangian/coalCombustion/submodels/surfaceReactionModel/COxidationKineticDiffusionLimitedRate/COxidationKineticDiffusionLimitedRate.C b/src/lagrangian/coalCombustion/submodels/surfaceReactionModel/COxidationKineticDiffusionLimitedRate/COxidationKineticDiffusionLimitedRate.C
index bb3e28ae56..078cd100d7 100644
--- a/src/lagrangian/coalCombustion/submodels/surfaceReactionModel/COxidationKineticDiffusionLimitedRate/COxidationKineticDiffusionLimitedRate.C
+++ b/src/lagrangian/coalCombustion/submodels/surfaceReactionModel/COxidationKineticDiffusionLimitedRate/COxidationKineticDiffusionLimitedRate.C
@@ -155,7 +155,7 @@ Foam::scalar Foam::COxidationKineticDiffusionLimitedRate::calculate
     dMassSRCarrier[CO2GlobalId_] += dmCO2;
 
     // Heat of reaction [J]
-    return HcCO2_*dmCO2;
+    return -HcCO2_*dmCO2;
 }
 
 
diff --git a/src/lagrangian/coalCombustion/submodels/surfaceReactionModel/COxidationMurphyShaddix/COxidationMurphyShaddix.C b/src/lagrangian/coalCombustion/submodels/surfaceReactionModel/COxidationMurphyShaddix/COxidationMurphyShaddix.C
index 128c5d64e9..265b4b6643 100644
--- a/src/lagrangian/coalCombustion/submodels/surfaceReactionModel/COxidationMurphyShaddix/COxidationMurphyShaddix.C
+++ b/src/lagrangian/coalCombustion/submodels/surfaceReactionModel/COxidationMurphyShaddix/COxidationMurphyShaddix.C
@@ -201,7 +201,7 @@ Foam::scalar Foam::COxidationMurphyShaddix::calculate
     dMassSolid[CsLocalId_] += dOmega*WC_;
 
     // Heat of reaction
-    return HcCO2_*dOmega*WC_;
+    return -HcCO2_*dOmega*WC_;
 }